Topic: Periodic Properties Question1: a) Write the name and chemical symbol of the element placed in second row and group 15 of the Periodic Table. b) Write the name and electronic configuration of the most electronegative element of the Periodic Table. c) Name the metalloid of the third period in the Periodic table. d) State the Modern Periodic Law. e) Define ionization potential. Question2: a) Why does metallic character decrease along a period as we move from left to right? Give 2 reasons. b) Why do inert gases have zero values of electron affinity? c) Why is the electron affinity of lithium higher than that of sodium? d) Though present in the same period, sodium is highly electropositive, while chlorine is highly electronegative. Give 2 reasons. Question 3: a) Distinguish between electron affinity and electronegativity. b) Why does atomic size decrease along a period from left to right? 39 K, write the atomic number and atomic mass number. Also calculate the ratio of 19 the number of neutrons to that of protons. c) For d) Arrange the elements Si, S, and P in the increasing order of electronegativity and the elements Na, Mg and Al in the decreasing order of atomic size. Question 4 Observe the table carefully and answer the questions given below: Li Be B C N O F Ne a) To which period of the Periodic Table does this set of elements belong? b) Arrange the above elements in the increasing order of electropositive character. c) Which of the above elements is an alkaline earth metal? d) Give the name of the element with the highest I.P in this period. --------------------------Topic: Chemical Bonding Question 1 Distinguish between the following terms: ( 1 point) : a) Electrovalency and Covalency : b) Dissociation and Ionsiation: c) Covalent bond and Co-ordinate covalent bond: Question 2: Draw the electron dot structures for the formation of the following : a) c) e) Nitrogen Magnesium chloride Ammonium ion g) the cation formed when an acid is dissolved in water. Question 3: b) Ammonia d) Calcium oxide f) Carbon tetrachloride Distinguish between ionic compounds and covalent compounds: a) Based on electrical conductivity b) Based on solubility: Question 4: Give reason/s: Ionic compounds are hard crystalline solids. Question 5: A certain period of the Periodic table is given below. The actual symbols of the elements have been replaced with some alphabets. C does not represent Carbon; H does not represent hydrogen while F represents fluorine. Observe the table carefully and answer the questions given below: Group1 Group 2 Group13 Group14 Group15 Group16 A B C D E X Group17 F Group18 Y a) Write the chemical formula of the compound formed between the elements B and X. b) Which element has the highest Ionisation Potential in this period? c) What is the valency of the element C? d) Identify the type of chemical bonding in the compound formed between the elements D and F. e) Draw the electron dot structure for the formation of the compound formed between the elements A and F. -------------------------------------------------------------- Topic: Analytical Chemistry Question 1 Write balanced chemical equations for the following chemical reactions and name the main product formed: a) The action of 2-3 drops of sodium hydroxide solution on calcium chloride solution --------------------------------------------------------------------------------------------------b) The reaction of aluminium with hot caustic soda solution --------------------------------------------------------------------------------------------------- c) The reaction of ammonium hydroxide with aqueous solution of iron (III) nitrate ------------------------------------------------------------------------------------------------d) The action of hot caustic potash solution on zinc hydroxide -------------------------------------------------------------------------------------------------e) The reaction of copper nitrate solution with a few drops of ammonia solution initially followed by excess of the reagent. _______________________________________________________________________ f) The reaction of lead nitrate solution with few drops of sodium hydroxide solution initially followed by excess of the reagent. Question 2 Write down the observation /s for the following chemical reactions: a) Ammonium hydroxide solution is added dropwise and then in excess to copper sulphate solution b) Sodium hydroxide solution is added dropwise and in excess to zinc sulphate solution ---------------------------------------------------------------------------------------------------------------------c) Zinc is reacted with hot caustic potash solution ___________________________________________________________________________ Question 3 Name / State the following: a) The oxides which can react with acids as well as bases to give salt and water:________ b) An oxide which is yellow in colour when hot and white in colour when cold._________ c) A cation which does not have a metal ion. _____________________ d) The chemical formula of the clear colourless salt solution formed when excess of sodium hydroxide is added to zinc chloride solution._____________ e) An orange coloured anion ____________________________ ---------------------------------------------------------- Question 4 : Using simple chemical tests and relevant chemical equations, distinguish between the following pairs of compounds: i) Calcium nitrate and lead nitrate ii) Copper (II) chloride and Iron (II) chloride iii) Zinc nitrate and lead nitrate ______________ Topic: Hydrogen chloride Question 1: Give balanced chemical equations for the following: a) The preparation of hydrogen chloride from rock salt. b) The action of dil HCl on marble chips. c) The reaction of lead (IV) oxide with conc. HCl d) The reaction of sodium thiosulphate with dil.HCl Question2: a) Give a chemical test to detect the presence of hydrogen chloride gas b) Give a chemical test to detect the presence of chloride ions in a salt. Give relevant equations and observations. c) Mention two properties of hydrogen chloride gas demonstrated by the Fountain experiment. ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------d) What are the advantages of the special funnel arrangement used to dissolve HCl gas in water? ______________________________________________________________________________ e) Why is it important to maintain temperatures less than 2000C in the preparation of hydrogen chloride gas from sodium chloride? ______________________________________________________________________________ Question 3: a) Why does hydrogen chloride gas fume in moist air? b) Name the drying agent used to dry hydrogen chloride gas. Why is this substance chosen as the drying agent for HCl? Why is quick lime not used to dry HCl gas? __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________ ________________________________________________________________________________ (c) Mention the mode of collection of HCl gas during its preparation from NaCl. State the reason(s) for the same. ________________________________________________________________________________ __________________________________________________________________________ d) Dry hydrogen chloride gas is neutral to litmus while an aqueous solution of hydrogen chloride turns blue litmus paper red. State the reason(s). _____________________________________________________________________________________ ___________________________________________________________________________________ Question 4: Write the observation/s for the following chemical reactions: a) A few drops of methyl orange are added to dilute hydrochloric acid. ____________________________________________________________________________ b) Sodium sulphite is treated with dil.HCl and heated. _______________________________________________________________________________ _____________________________________________________________________________ c) Dilute Hydrochloric acid is heated with iron (II) sulphide. _______________________________________________________________________________ _______________________________________________________________________________ d) An aqueous solution of lead nitrate is added to dil.HCl. _______________________________________________________________________________ Question 5 Using a chemical test, how will you distinguish between Manganese dioxide and Copper ( II ) oxide? (two observations ). Give relevant chemical equations. _______________________________________ Topic: Ammonia Question 1: Write balanced chemical equations for the following chemical reactions: a) The industrial process of manufacture of ammonia _____________________________________________________________________ b) The laboratory preparation of ammonia from sal ammoniac and slaked lime a) The action of water on calcium nitride and aluminium nitride respectively b) The catalytic oxidation of ammonia c) The reaction of ammonia with heated copper (II) oxide d) The reaction of excess ammonia with chlorine Question 2: a) Give two colour tests to detect the presence of ammonia, giving relevant observation/s: a. Write the properties of ammonia demonstrated by the fountain experiment. -----------------------------------------------------------------------------------------------------b. Name the apparatus used to dissolve ammonia gas in water. -----------------------------------------------------------------------------------------------------c. During the preparation of ammonia in the laboratory, how is it confirmed that a glass jar is full of ammonia? ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------d. Why are optimum temperatures employed in Haber’s process? -----------------------------------------------------------------------------------------------------e. Why is dry ammonia gas is neutral to dry litmus? ___________________________________________________________________ __________________________________________________________________ Question 3: Give relevant observation/s for the following chemical reaction/s: a) Ammonia is passed over lead (II) oxide. b) Ammonia is burnt in oxygen c) Ammonia is reacted with excess chlorine d) A few drops of methyl orange are added to ammonium hydroxide Topic : Nitric acid Answer the following questions: Question 1: Write balanced chemical equations for the following: a) Preparation of nitric acid from nitre --------------------------------------------------------------------------------------------------------b) Reaction of manganese with very dilute, cold nitric acid -------------------------------------------------------------------------------------------------------c) Action of hot concentrated nitric acid on sulphur -------------------------------------------------------------------------------------------------------d) Reaction between baking soda and dilute nitric acid Question 2: Give your observation/s for the following: a) Concentrated nitric acid is poured over copper turnings. --------------------------------------------------------------------------------------------------------b) Sodium sulphite is treated with dilute nitric acid -------------------------------------------------------------------------------------------------------c) Hot concentrated nitric acid is added to saw dust kept in a porcelain dish. -------------------------------------------------------------------------------------------------------d) A few drops of methyl orange are added to nitric acid Question 3 Write the equations involved in the industrial preparation of nitric acid (Ostwald’s process) ______________________________________________________________________________ Question 4: Name the following: a) The compound which constitutes the brown ring in the chemical test used for the detection of nitrate radical. -------------------------------------------------------------b) The yellow coloured compound formed when nitric acid comes in contact with our skin ------------------------------------------------c) The process of conversion of atmospheric nitrogen into useful nitrates which can be used by plants. -------------------------------------------------Question 5: Give reason/s for the following: a) An all glass apparatus is used in the laboratory preparation of nitric acid from nitre. ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------b) Nitric acid prepared in the laboratory is yellow in colour.. ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Topic: Sulphuric acid Answer the following questions: Question 1: Write balanced chemical equations for the following: a) Catalytic oxidation of sulphur dioxide in Contact process --------------------------------------------------------------------------------------------------------b) Reaction of copper with conc. sulphuric acid -------------------------------------------------------------------------------------------------------c) Action of dilute sulphuric acid on washing soda -------------------------------------------------------------------------------------------------------d) Reaction of conc. sulphuric acid with copper sulphate pentahydrate crystals ---------------------------------------------------------------------------------------------------------Question 2: Give your observation/s for the following: a) Concentrated sulphuric acid is added to glucose --------------------------------------------------------------------------------------------------------b) Sodium sulphite is treated with dilute sulphuric acid -------------------------------------------------------------------------------------------------------c) A few drops of alkaline phenolphthalein are added to dilute sulphuric acid -------------------------------------------------------------------------------------------------------d) Zinc granules are added to dilute sulphuric acid Question 3: Give reason/s for the following: a) Sulphur trioxide is not absorbed in water during the industrial preparation of sulphuric acid ------------------------------------------------------------------------------------------------------ -----------------------------------------------------------------------------------------------------------b) An optimum temperature is used for the oxidation of SO2 to SO3 during Contact process. ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------________________________________________________________________________ c) When concentrated sulphuric acid comes in contact with our skin , charring of our skin occurs --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- d) Vanadium pentoxide is preferred to platinised asbestos as a catalyst in Contact process ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------Question 4 Write the role of sulphuric acids in the following chemical reactions. Also give the balanced chemical equations for the chemical reactions. a) reaction zinc with dil sulphuric acid: b) reaction zinc with conc. sulphuric acid: c) action of conc. sulphuric acid on blue vitriol d) reaction of conc. sulphuric acid with nitre e) reaction of sodium sulphide with dilute sulphuric acid Question 5 Write the balanced chemical equations for the following chemical reactions Concentrated sulphuric acid is poured over canesugar. _____________________ Topic: Acids, Bases and Salts Question 1: Give balanced chemical equations for the following: i) Preparation of Lead (II) chloride from Lead (II) oxide (2 steps) ____________________________________________________________ ------------------------------------------------------------------------------------------iii Neutralization of iron (III) hydroxide using dilute nitric acid -----------------------------------------------------------------------------------------v) The decomposition of ammonium carbonate using dilute sulphuric acid ----------------------------------------------------------------------------------------Question 2: Write the observation/s for the following chemical reactions: i) Copper oxide is treated with dilute sulphuric acid ----------------------------------------------------------------------------------------ii) Washing soda crystals are left exposed to air for a few days. __________________________________________________________ iii) aqueous solutions of calcium chloride and sodium carbonate are mixed together and stirred -------------------------------------------------------------------------------------Question 3. Classify the following as acidic, basic or normal salts. Support your answer with the definition of the type of salt: i) NaHSO4 ii) Zn (OH)Cl iii) Na3PO4 Question 4. Define the following: i) Water of crystallization: ___________________________________________________________________ ________________________________________________________________________ ii) Deliquescence: ______________________________________________________________ ________________________________________________________________________ Question 5: Complete the following table: Name of the salt Blue vitriol Glauber’s salt Name of the method of preparation i) Equation ii) Decomposition of carbonate ii) i) NaOH+ i) Mistakes to be avoided Cu + H2SO4 Na + H2SO4 OR Na2CO3 + Zinc sulphate ii) Decomposition of carbonate / bicarbonate i) OR ii) Iron (II)sulphate Iron (III) chloride Lead sulphate from Lead carbonate 2 steps: Pb + H2SO4 i) i) ii) ii) Question 6. Classify the following as hygroscopic, deliquescent or efflorescent: Calcium oxide, fused calcium chloride, conc,. sulphuric acid, Galuber’s salt, blue vitriol, silica gel , phosphorus pentoxide. Hygroscopic: Deliquescent : Efflorescent: ________________________________________________________ Topic: Electrolysis Question1 Write the electrode reactions for the following: i) Electrolysis of acidified water using platinum electrodes Cathode:------------------------------- ii) Anode:---------------------------------------------- Electrolysis of fused lead bromide using graphite electrodes Cathode:------------------------------iii) Electrolysis of fused NaCl using graphite electrodes Cathode:------------------------------- iv) Anode:--------------------…………. Anode:------------------------------------------------ Electrolysis of aqueous copper sulphate using copper electrodes Cathode:------------------------------- Anode:----------------------------------------------- Question 2 Distinguish between the following: (any two points): i) cathode and anode ii) strong electrolyte and weak electrolyte Question 3: Define the following: i) Electrolysis: ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- ii) Electroplating: -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Question 4: Give your observation/s for the following ( at both the electrodes and in the electrolyte, if any) : i) Copper sulphate solution is electrolysed using copper electrodes. ii) Fused lead bromide is electrolysed using graphite electrodes. Question 5: Give reason/s for the following: i) Dilute sulphuric acid is added to distilled water before subjecting it to electrolysis _____________________________________________________________________ ii) Sodium argentocyanide solution is preferred to silver nitrate solution as the electrolyte in the electroplating of silver. ________________________________________________________________________ _______________________________________________________________________ Question 6: Name the following: i) The cathode in the electroplating of an iron nail with nickel: ------------------------ii) The anode in the electroplating of an article with silver: ----------------------------- iii) The cathode in the electrorefining of copper: -------------------------------------------- iv) The electrolyte used in the electrorefining of copper: ---------------------------------- Topic: Mole Concept and Stoichiometry Set 1: Problems based on Gay Lussac’s Law: 1. Nitrogen and hydrogen react to give ammonia. Calculate the volume of ammonia formed when nitrogen reacts with 9 litres of hydrogen, all volumes being measured at S.T.P. Ans: [ 6 lit of ammonia) 2. 250 cm3 of carbon monoxide and 100 cm3 of oxygen are ignited together. Calculate the composition of the resulting mixture. Ans: [ 50 cm3 of carbon monoxide , 200 cm3 carbon dioxide, 0 cm3 oxygen] 3. What volume of oxygen would be required to burn completely 300 ml of ethylene (C2H4) ? Also determine the volume of carbondioxide formed? (Ans: 900 ml oxygen, 600 ml carbondioxide) 4. 2500 cc of oxygen was burnt with 600 cc of ethane (C2H6). Calculate the volume of unused oxygen and the volume of carbon dioxide formed. Ans: [ unused oxygen = 400 cc, volume of carbon dioxide = 1200 cc) 5. 100 cc each of water gas and oxygen are ignited and the resulting gases cooled to room temperature. Calculate the composition of the resulting mixture. (Water gas contains CO and H2 in equal ratio) Ans: [ 50cc unused oxygen, 50 cc of carbondioxide 6. LPG stands for Liquified Petroleum gas. A certain variety consists of 60% propane and 40% butane.. If 10 litres of this mixture is burnt, calculate the volume of carbon dioxide added to the atmosphere. The combustion reactions are given as follows: C3H8(g) + 5O2(g) → 3CO2(g) + 4H2O(g) 2C4H10(g) + 13O2(g) → 8CO2(g) + 10H2O(g) [Ans: 18 + 16 =34 lit carbon dioxide) 7. On igniting a mixture of acetylene and oxygen, 200 cm3 of CO2 is collected at S.T.P. Calculate the volume of acetylene and oxygen in the original mixture. [Ans; 100 cm3 acetylene, 250 cm3oxygen] 8. Ethane burns in air forming carbon dioxide and water vapour. Calculate the volume of air required to burn 100 cm3 ethane. Assume air contains 20% oxygen. [Ans; 1750 cm3] 9. 100 ml of ethylene is burnt in just sufficient air ( containing 20% oxygen) as per the equation C2H4 + 3O2 → 2CO2 + 2H2O(g). Calculate the resultant mixture composition at 1000C and constant pressure. Ans: 1200 ml nitrogen , carbon dioxide = 200 ml , water vapour = 200 ml, ethylene and oxygen= 0 ml] 10. 67.2 lit of hydrogen combines with 44.8 lit of nitrogen to form ammonia under specific conditions: N2 (g) + 3H2 (g) → 2NH3(g) Calculate the volume of ammonia produced. What is the other substance, if any , that remains in the resultant mixture? Ans: 44.8 lit of ammonia is produced, 22.4 lit of nitrogen remains 11. Calculate the volume of oxygen required for the complete combustion of 8.8 g of C3H8 ie.,propane. ( atomic mass of C=12, H=1, O=16) C3H8 + 5O2 → 3CO2 + 4H2O(g). Ans: 22.4 dm3 of oxygen Set 2: Problems based on Avogadro’s Law: 1. Three gases A, B and C are maintained under similar conditions of temperature and pressure. If 200 ml of a gas A contains ‘X’ molecules, how many molecules will be present in a) 100 ml of gas B b) 50 ml of gas ‘C’. ( Answer in terms of X) Ans: X / 2 molecules of B b) X / 4 molecules of C 2. Three gases namely CO2, SO2 and H2 contain the same number of molecules ‘X’. If CO2 occupies ‘Y’ litres, state the volume occupied by a) X molecules of SO2 b) 2X molecules of H2 Ans: a) Y litres of CO2 b) 2Y litres of H2 3. The volumes of gases A, B and C are in the ratio 1 : 2: 3 under similar conditions of temperature and pressure. a) Which gas contains the maximum number of molecules? b) What will happen to the volume of the gas A if the number of molecules is tripled , provided the temperature and pressure of A are kept constant. c) If volume of A is 11.2 litres at S. T.P, calculate the number of molecules of the gas B at S.T.P.. Ans: a) Gas C b) Tripled c) 6.023 × 1023 molecules Set 3: Problems based on Vapour density and Molecular weight: 1. Calculate the atomicity of a gas [at. wt. 35.5 ] whose vapour density is equal to its relative atomic mass. Ans: 2 2. A gas cylinder of capacity 40 dm3 is filled with gas X , the mass of which is 20 g. When the cylinder is filled with hydrogen gas at the same temperature and pressure, the mass of hydrogen is 4 g. Determine the vapour density and relative molecular mass of the gas X. Ans: V.D = 5, relative molecular mass = 10. 3. A gas cylinder holds 70 g of gas X. The same cylinder when filled with hydrogen holds 7.0 g of hydrogen under the same conditions of temperature and pressure. Determine the gram molecular weight of the gas X. Ans: 20 g 4. 500 ml of a gas X at S.T.P weighs 0.50 g. Calculate the vapour density and molecular weight of the gas . Given that 1 litre of hydrogen at S.T.P weighs 0.09g. Ans: 11.1, 22.2 g Set 4: Problems based on moles , RMM , GMV and Avogadro number: 1. Calculate the number of moles ( gram molecules) in a) 8 grams oxygen b) 90g water c) 1.6 grams helium d) 2.2 grams CO2. Given the atomic weight of H=1, O= 16, C= 12, He = 4 ) Ans: a) 0.25 b) 5 c) 0.4 d) 0.05 2. Calculate the number of molecules in a) 7 grams of nitrogen b) 32 grams of methane c) 5.85 g sodium chloride. Given at wt of Na = 23, Cl = 35.5, N= 14, C=12, H=1. Ans: a) 0.25 × 6.023 × 1023 b) 2.0 × 6.023 × 1023 c) 0.1 × 6.023 × 1023 3. Calculate the number of molecules and atoms in a) 0.25 moles of chlorine b) 196 g of sulphuric acid. At wt of Cl=35.5, mol.wt of sulphuric acid =98] Ans: [ a) 0.25 × 6.023 × 1023 molecules, 0.5 × 6.023 × 1023 atoms of chlorine b) 2× 6.023 × 1023 molecules, 14× 6.023 × 1023 atoms of sulphuric acid] 4. Calculate the weight ( in grams) of a) 5.5 moles of hydrogen b) 2.5 moles of CO c) 1.5 × 6.023 × 1023 molecules of water d) 3.0115 × 1023 molecules of oxygen e) 6.023 × 1022 molecules of calcium carbonate. Given atomic weight of H=1, C=12, O=16, Ca= 40, S= 32 Ans: a) 11.0 g hydrogen b) 70 grams CO c) 27 g water d) 16 grams oxygen e) 10 grams calcium carbonate 5. Calculate the a) number of gram molecules b) number of gram atoms in 35.5 grams chlorine. Atomic wt of Cl = 35.5 Ans: a) 0.5 b) 1. 0 6. Calculate the number of moles of chloride ions and calcium ions which will be obtained from 222 grams of calcium chloride. [ Ca= 40, Cl= 35.5] Ans: 2 moles of calcium ions and 4 moles of chloride ions] 7. Calculate the volume at S.T.P of a) 1.5 moles of hydrogen b) 3.2 grams SO2 c) 6.023 × 1022 molecules of ethylene. At. wt of S=32, O=16, C=12, H=1. Ans: a) 33.6 dm3 b) 0.05 × 22.4 = 1.12 dm3 c) 2.24 dm3 8. Calculate a) the mass of oxygen gas which occupies a volume of 11.2 dm3 at S.T.P. b) the number of moles present in 5.6 litres at S.T.P of hydrogen c) the number of molecules present in 2.24 lit of nitrogen . Ans: a) 16 g b) 0.25 moles c) 6.023 × 1022 molecules of nitrogen 9. 50 grams of hydrogen , oxygen and sulphur dioxide are taken separately in three different cylinders P, Q and R. a) Which cylinder contains the highest number of moles of the gas? b) Which cylinder contains the least number of gas molecules? [At wt O=16, H=1, S=32]. Ans: a) P b) R 10. Calculate the atomicity of a gas ‘X’ if 1 g of ‘X occupies 11,200 cc at S.T.P . Given that atomic weight of ‘X’ =1. Ans: Atomicity =2. 11. Calculate the mass of 1022 atoms of sulphur . Given atomic weight of sulphur = 32 and Avogadro number = 6 × 1023 Ans: 0.53 grams 12. Calculate the relative molecular mass and vapour density of benzene (C6H6) if 390 grams of the liquid on vaporization has a volume of 112 litres at S. T.P. Ans: R.M.M = 78, V.D = 39 13. A gas occupies a volume of 100 cc at S.T.P and weighs 0.5 grams . Find its RMM. Ans: 112. 14. The mass of 5.6 dm3 of a certain gas at S.T.P is 12.0g. Calculate the relative molecular mass of the gas. Ans: 48 ------------------------------------------------------------------------------------------------------------- Stoichiometry Set 5: Problems based on percentage composition 1. Calculate the percentage by weight of a) calcium in calcium carbonate b) oxygen in hydrogen peroxide c) potassium in potassium dichromate [H=1, O=16, Ca= 40, C=12,K=39. Cr=52] Ans: a) 40%, b) 94.11% c) 26.53% 2. Calculate the percentage of water of crystallization in Glauber’s salt (Na2SO4.10H2O). [ Na =23, S=32, O=16, H=1] Ans: 55.90% 3. What is the mass of nitrogen in 1000 kg of urea whose molecular formula is CO(NH2)2? [ C=12, H=1, N=14, O=16] Ans: 466 kg. 4. Calculate the mass of nitrogen supplied to the soil by 5kg of urea ( molecular formula is CO(NH2)2 ). [ C=12, H=1, N=14, O=16] Ans: 2333.3 g 5. Which is a better fertilizer : Urea or ammonium phosphate? [N=14, C=12, H=1, O=16, P =31] Ans: Urea as it has a higher percentage of nitrogen ( N= 46.67% as compared to 28.19% in ammonium phosphate) 6. Calculate the percentage of pure aluminium in 10 kg of aluminium oxide (Al2O3) of 90% purity. [ Al=27, O=16] Ans: 47.64% 7. Hydrated Calcium sulphate [CaSO4.xH2O] contains 21% water of crystallization. Calculate the number of molecules of water of crystallization. ie. ‘x’ in the hydrated salt. [Ca= 40, S= 32, H=1, O=16] Ans: CaSO4.2H2O 8. Calculate the number of molecules of water of crystallization in copper sulphate crystals, if 10g of hydrated copper sulphate crystals gives 6.4g of anhydrous copper sulphate on heating. [Cu=64, s= 32, O=16] Ans: 5 molecules Set 6: Calculation of Empirical formula and Molecular formula of compounds: 1. Calculate the molecular formula of a compound whose empirical formula is CH2O and vapour density is 90. Ans: C6H12O6 2. Write the empirical formula of a) benzene (C6H6) b) Octane ( C8H18) Ans: a) CH b) C4H9 3. A compound has C= 57.82%, O = 38.58% and the rest hydrogen. Its vapour density is 83. Determine its empirical formula and molecular formula.[C=12, H=1, O=16] Ans: C4H3O2, C8H6O4 4. A metal ‘M’ forms a volatile chloride containing 65.5% chlorine. If the density of the chloride relative to hydrogen is 162.5, find the molecular formula of the chloride. [ M=56, Cl =35.5 ] Ans: molecular formula= M2Cl6 5. A compound has the following percentage composition by mass : C= 14.4%, H=1.2% and Cl=84.5%. Determine the empirical formula of the compound. The relative molecular mass of the compound is 168. Determine the molecular formula of the compound.[ C=12, H=1, Cl=35.5]. Ans: CHCl2, C2H2Cl4 6. A compound has the following percentage composition: Zn=22.65%, S=11.15%, O= 61.32% and H= 4.88%. Its relative molecular mass is 287. Calculate its molecular formula assuming that all the hydrogen atoms in the compound are present as water of crystallization in combination with oxygen.[ Zn=65, S= 32, O=16, H=1] Ans: ZnSO4.7H2O Set 7: Problems on Chemical Equations 1. Determine the volume of hydrogen gas which will be obtained at S.T.P by the action of 3.275 g of zinc with excess dilute hydrochloric acid. [Zn= 65.5] Ans: 1.12 dm3 2. What will be the volume of oxygen obtained at S.T.P by the decomposition of 61.25g potassium chlorate (KClO3)? The equation for the decomposition of potassium chlorate is 2KClO3 → 2KCl + 3O2↑ [K=39, Cl=35.5, O=16] Ans: 16.8 dm3 3. From the equation, 3Cu + 8HNO3 → 3Cu(NO3)2 + 4H2O + 2NO↑. Calculate a) The mass of copper needed to react with 12.6 grams of nitric acid. b) The volume of nitric oxide collected at the same time at S. T.P. [Cu=63, H=1, O=16, N=14] Ans: a) 4.8g b) 1.12 dm3 4. Calculate the weight of potassium nitrate which should be heated to produce 5600c.c of oxygen gas at S.T.P. [K=39, O=16, N=14]. 2KNO3 → 2KNO2 + O2↑. Ans: 50.50 g 5. A sample of ammonium nitrate yields 8.96 litres of steam at S.T.P. NH4NO3 → N2O ↑ + 2H2O↑. a) What volume of nitrous oxide is produced at the same time as 8.96 litres of steam? b) What mass of ammonium nitrate should be heated to produce 8.96 litres of steam? [relative molecular mass of ammonium nitrate is 80] Ans: 4.48 litres, 16 g] 6. P + 5HNO3 → H3PO4 + H2O + 5NO2↑. a) What mass of phosphoric acid can be prepared from 6.2g of phosphorus? b) What mass of nitric acid will be consumed at the same time? c) What would be the volume of steam produced at S.T.P at the same time? [H=1, N=14, O=16, P=31] Ans: a) 19.6g b) 63g c) 4.48 lit Topic: Organic Chemistry Set I – Nomenclature 1. CH3 –CH2 –CH2 –CH3 IUPAC name: Common name: Note: 2. CH3 – CH3 │ CH –CH3 IUPAC name: Common name: Note: 3. CH3 –CH2 –CH2 – CH2 –CH3 IUPAC name: Common name: 4. CH3 │ CH3 – CH2–CH –CH3 IUPAC name: Common name: Note: 5. CH3 │ CH3 –C–CH3 │ CH3 Note: IUPAC name: Common name: C2H5 │ 6. CH3 –CH2–CH – CH3 Note: CH3 │ 7. CH3 – CH2 C –CH3 │ CH3 OH │ 8. CH3 – CH2–CH –CH3 IUPAC name: IUPAC name: IUPAC name: Note: CH3 OH │ │ 9. CH3 – CH–CH –CH3 Note: CH3 OH │ │ 10. CH3 – CH–CH –CH3 Note: C2H5 OH │ │ 11. CH3 – CH–CH2-CH –CH3 Note: IUPAC name: IUPAC name: IUPAC name: Br Cl │ │ 12. CH3 – CH–CH2 – CH- CH3 Note: IUPAC name: 13. CH3 – CH2 – CH - CH- CH2 CH2 CH3 │ │ CH3 C2H5 IUPAC name: Note: CH3 Cl │ │ 14. CH3 – CH–CH2 – CH - CH3 IUPAC name: Note: Cl │ 15. CH3 CHCH=CH2 IUPAC name: Note: CH3 │ 16. CH3 –CH2 –C =CH2 IUPAC name: Note: 17. CH3 CH2CHBr2 Note: IUPAC name: CH3 │ 18. CH3–C -Cl │ CH3 IUPAC name: Note: 19. CH3 –C = C-CH3 │ │ Br C2H5 Note: CH3 │ 20. CH3 –C C-CH2 –CH –CH3 Br Br │ │ 21. CH3 – C –C-CH3 │ │ Br Br 22. C2H5 CH2 CH CH2OH │ CH3 CH3 H │ │ 23. CH3- C - C -OH │ │ CH3 H 24. C2HCl5 IUPAC name: IUPAC name: IUPAC name: IUPAC name: IUPAC name: IUPAC name: Cl Cl │ │ 25. H-C =C –H IUPAC name: 26. CH2-CH2 27. CH3 CH2 Br OH OH IUPAC name: 29. CH3 –C C- CH –CH3 IUPAC name: name: IUPAC name: 30. CH3CH2 CH2 CHO IUPAC name: 28. CH2Cl2 IUPAC name: 31. HCOOH IUPAC name: Set II – Writing Condensed and Branched Structural formula S.No. Name of the compound 1. Pentane 2. 2,2 –dimethyl propane 3. 2-methyl but-2-ene 4. 4-methyl-pent-1-yne 5. 3-methyl pentan-2-ol 6. 1,2 -dibromoethene 7. 2-methyl butanal 8. 2-chloro propanoic acid 9. Acetone 10. Acetaldehyde Condensed structural formula Branched structural formula 11. Formic acid 12. Diethyl ether 13. Ethyl acetate 14. Ethyl bromide Set III – Chart of various Homologous Series Homologous Series: Alkanes or Paraffins; Molecular formula Condensed structural formula Gen.formula: Branched structural formula Root + word Functional Gp : Sec = IUPAC suffix name Common Or Trivial name n=1 n=2 n=3 n=4 n=5 Homologous Series: Alkenes or Olefins ; Molecular formula n=2 n=3 n=4 Condensed structural formula Gen.formula: Branched structural formula Root + word Functional Gp : Sec = IUPAC suffix name Common Or Trivial name Homologous Series: Alkynes ; Molecular formula Condensed structural formula Gen.formula: Branched structural formula ; Functional Group : Root + word Sec = IUPAC suffix name Common Or Trivial name n=2 n=3 n=4 Homologous Series: Alcohols ; Molecular formula n=1 n=2 n=3 n=4 Condensed structural formula Gen.formula: Branched structural formula ; Functional Group : Root + word Sec = IUPAC suffix name Common Or Trivial name Homologous Series: Aldehydes ; Molecular formula Condensed structural formula Gen.formula: Branched structural formula ; Root + word Functional Group : Sec = IUPAC suffix name Common Or Trivial name n=1 n=2 n=3 Homologous Series: Ketones ; Molecular formula Condensed structural formula Gen.formula: Branched structural formula ; Root + word Functional Group Sec = IUPAC suffix name : Common Or Trivial name n=3 n=4 Homologous Series: Carboxylic acids ; Molecular formula n=1 n=2 n=3 Condensed structural formula Gen.formula: Branched structural formula Root + word Functional Gp : Sec = IUPAC suffix name Common Or Trivial name Homologous Series: Carboxylic Esters ; Molecular formula Condensed structural formula Branched structural formula Functional Group : Root + word Sec = IUPAC suffix name Common Or Trivial name n=2 n=3 n=5 Homologous Series: Ethers ; Molecular formula Condensed structural formula General Formula Branched structural formula Functional Gp :: Root + word Sec = IUPAC suffix name Common Or Trivial name n=2 n=3 Homologous Series: Alkyl halides ; Molecular formula n=1 n=2 Condensed structural formula Gen. Formula: Branched structural formula ; Root + word F.G : Halo ( -Cl, -Br, -I, -F) Sec = IUPAC suffix name Common Or Trivial name Set IV – Isomerism Write the branched structural formulae of the isomers of the compounds with the given molecular formulae. Write their IUPAC and Common names( wherever applicable): 1. C4H10 2. C5H12 3. C4H8 4. C4H6 Pawar Public School, Bhandup Chemistry worksheet 1. Topic: Alkanes, Alkenes and Alkynes Write the structural formula ,the IUPAC and Common names of the isomers of the compounds represented by the following molecular formulae: a) C5H12 Structural formula: i) ii) iii) IUPAC name : IUPAC name : IUPAC name : Common name: Common name: Common name: b) Write the structural formula and the IUPAC name of : i) a chain isomer of n hexane ii) a position isomer of 1- pentyne c) Draw the electron dot structures of Ethane Ethylene 2) Give balanced chemical equations for the preparation of : i) Ethane from sodium propionate ii) Methane from methyl iodide Acetylene iii) Ethane from Iodomethane 3) Write the balanced chemical equations with the necessary conditions for the 4 steps involved in the photochlorination of methane. Give the IUPAC names of the products formed in each stage. _____________________________________________________________________ Overall reaction: 4) Write the balanced chemical equations for the stepwise oxidation of: i) Ethane using acidified potassium dichromate ii) Methane using heated copper as catalyst iii) 5. 6. Ethane using heated Molybdenum oxide catalyst Write balanced chemical equations for the following: i) the complete combustion of ethane ii) the incomplete combustion of methane iii) the pyrolysis of methane iv) the pyrolysis of ethane How will you prepare ethylene from: ( Give balanced equations with conditions; no description needed) : i) Ethanol ii) Bromoethane: 7. How will you bring about the following conversions: ( only equations) : i) Ethene to ethane ii) Ethene to 1,2 – dibromoethane iii) Ethylene to ethyl bromide iv) Ethyl bromide to ethylene v) Ethene to ethylene glycol 8. Write balanced chemical equations for the following conversions: i) Calcium carbide to ethyne ii) 1, 2- dibromoethane to ethyne iii) Ethyne to ethane iv) Ethyne to 1,1,2,2 – tetrabromoethane 9. Write your observation(s) for the following chemical reactions: i) Ethylene is passed into bromine in carbon tetrachloride ii) Acetylene is passed into ammoniacal cuprous chloride solution iii) Acetylene is passed into ammoniacal silver nitrate solution iv) Ethene is passed into cold alkaline solution of potassium permanganate 10. Give a chemical test to distinguish between the following pairs of compounds: i) Ethane and Ethene ii) Ethene and Ethyne 11. Write the structural formulae and the IUPAC name of the 2 isomers represented by the formula C3H7OH. 12. Write the structural formulae and the IUPAC name of the 4 isomers represented by the formula C4H9OH. 13. Write balanced chemical equations for the following: i) The action of aqueous KOH on bromoethane ii) The action of alcoholic KOH on bromoethane iii) The complete combustion of ethanol iv) The complete oxidation of ethanol using acidified potassium dichromate ( 2 steps) v) The dehydration of ethyl alcohol vi) The reaction of ethanol with sodium ( write observation also) vii) The reaction of ethanol with acetic acid and conc sulphuric acid ( write observation also) 14. What is meant by the terms ‘Denatured alcohol’ and ‘Methylated spirit’? 15. What is meant by esterification? Explain with an example . Mention the role played by conc. Sulphuric acid. 16. Give a chemical test in which i) An alcohol resembles a carboxylic acid ii) An alcohol differs from a carboxylic acid. 17. Write balanced chemical equations for the following : 18. i) Preparation of ethanoic acid from ethanol ( 2 steps) ii) Reaction of ethanoic acid with calcium What is meant by ‘glacial acetic acid’? 19. Write two main uses each of methane, ethane, ethane and ethyne. Methane: Ethane: Ethene: Ethyne: 20. Write four important uses of i) ethyl alcohol _______________________ ii) acetic acid. METALLURGY - I I. Group No. 1 or IA 2 or IIA Position of Metals in the Periodic Table Type of Elements Alkali metals Alkaline earth metals Elements Li, Na, K, Rb, Cs, Fr Be, Mg, Ca, Sr, Ba, Ra Property Light & soft metals Low melting points 3 to 12 Transition metals Fe , Zn, Cu, Ag 13 to 16 Post transition elements Al Reason Highly electropositive & reactive and strong reducing agents Heavy & hard metals High melting points Not highly electropositive Weakly electropositive Have large atomic size, hence low density. Forces binding the atoms are weak. Have low ionization potentials due to large atomic size. So valence electrons can be easily removed from the outermost shell. Have small atomic size, hence high density. Forces binding the atoms are strong. Comparatively high ionization potentials which increases across the period. Smaller atomic size & have higher ionization potential. So lesser tendency to lose valence electrons. II. Comparison of Metals & Non-metals – Physical properties Property Physical state Metals Solids at room temperature Lustre Lustrous – can be polished Hardness Hard solids Melting & Boiling points High Density High Malleability Malleable – Can be beaten into sheets Ductile – can be drawn into wires Good conductors of electricity Good conductors of heat High Ductility Conductivity Tensile strength Sonority Solubility Alloying Exceptions Mercury & Gallium are liquids at room temperature --- Non - metals Liquids, gases or brittle solids Sodium, Potassium, Lead & Mercury (liquid) Sodium, Potassium & Mercury – Low M.P & B.P Sodium, Potassium & Calcium – Low density Zinc Soft solids --- Graphite & Iodine show luster. (Iodine is subliming solid) Diamond (carbon) Low Carbon & Silicon – High M.P & B.P Low Diamond (carbon ) – High density Non - malleable Carbon fibre Zinc & Mercury Non - ductile Carbon fibre Tungsten Non – conductors of electricity Poor conductors of heat Low Graphite and Gas Carbon Not sonorous -- Soluble in water or solvents (No occurrence of chemical change on dissolution) Do not form Carbon (in steel) Zinc & Mercury Sonorous – gives Sodium & a note on striking Potassium Insoluble in water or solvents (Occurrence of chemical change on dissolution) Form alloys Non - lustrous Exceptions Carbon fibre alloys III. Comparison of Metals & Non-metals –Chemical properties Property Electronic configuration Atomicity Ion formation On electrolysis Reducing – Oxidising nature Reaction with acids Nature of oxides Nature of chlorides Metals 1, 2 or 3 valence electrons Monoatomic Non - metals {4} 5, 6, or 7 valence electrons Diatomic, triatomic or polyatomic Noble gases are monoatomic Lose valence electrons & form cations Gain electrons & form anions Electropositive in nature Electronegative in nature Cations move towards cathode accept Anions move towards anode lose electrons & get discharged as neutral electrons & get discharged as atoms (undergo reduction) neutral atoms or molecoles (undergo oxidation) Reducing agents – Donate electrons Oxidising agents – Accept during chemical reactions electrons during chemical reactions Active metals react with dilute acids Non - metals do not react with (dil. HCl or dil. H2SO4) to liberate dilute acids (dil. HCl or dil. H2SO4) hydrogen to liberate hydrogen Form basic oxides {eg: K2O, Form acidic or neutral Na2O, CaO, CuO,MgO, Fe2O3} oxides Soluble basic oxides dissolve in Soluble acidic oxides water to give alkaline solutions dissolve in water to give {eg : K2O, Na2O,MgO, CaO} acidic solutions Metallic oxides are Non – metallic oxides are electrovalent covalent Acidic – CO2, SO2, SO3, Oxides of Al, Zn & Pb are NO2, P2O5 amphoteric – They react with Neutral – CO, NO, N2O, acids as well as alkalis to give H2O salt & water. Form electrovalent chlorides Form covalent chlorides They are non – volatile solids They are volatile liquids(eg o Eg : NaCl, KCl : PCl3) or solids(eg : PCl5) They are soluble in water They are insoluble in water IV. Comparison of General characteristics of Alkali metals & Alkaline earth metals Characteristics Position Elements Valence electrons Occurrence Nature & Bonding Density Melting point & Boiling point Flame test Reactivity Action of air Action of water Action of acids Alkali metals Group 1 [IA] Li, Na, K, Rb(Rubidium), Cs(Cesium) & Fr(Francium) One Highly reactive Occur in combined state only Compounds of Na & K are most abundant Francium is radioactive & occurs in traces Silvery white Soft in nature [can be cut with knife] Have a single valence electron & metallic bonding is not so strong Alkaline earth metals Group 2 [IIA] Be, Mg, Ca, Sr(Strontium), Ba(Barium), Ra(Radium) Two Reactive Occur in combined state only Compounds of Mg & Ca are most abundant Radium is radioactive & is a rare element Silvery white Slightly harder than alkali metals Have two valence electrons & metallic bonding is stronger than that in alkali metals Low Higher Low Higher Characteristic colour given to Be & Mg do not give a flame characteristic colour Sodium – golden yellow Calcium – brick red, flame, potassium – lilac flame Strontium – crimson / scarlet red, Barium – apple green flame. Strongly electropositive & Less electropositive & less highly reactive reactive On exposure to moist air On exposure to moist air tarnish rapidly {except Li} tarnish slowly {except Be} Hence they are kept under kerosene React with cold water Be does not react with water. vigorously liberating hydrogen Mg reacts with boiling water. Ca, Sr, Ba react with cold water. React with acids vigorously React with acids less displacing hydrogen. vigorously displacing hydrogen. Topic: Metallurgy – Part 2 Uses of Aluminium: i) Household purposes: Aluminium metal is used to make utensils for cooking. Reasons: Aluminium metal is light, a good conductor of heat, corrosion resistant, unaffected by food acids and less expensive compared to many other metals and alloys. ii) Packaging: Thin aluminium foils are used in food packaging , packaging of medicines and in the manufacture of photographic films.. Reasons: Aluminium metal is light, corrosion resistant, has a bright appearance and is cheap. iii) Paints: A mixture of aluminium powder and linseed oil is used to make paints for electric poles. (anti corrosive paints) . Reasons: Aluminium is corrosion resistant. It is used to prevent the corrosion of iron. iv) Electrical Cables Aluminium wires are used as cable and transmission wires. Reasons: Aluminium is a good conductor of electricity. v) Alloys: The alloys of aluminium like Duralumin and Magnalium are used in the manufacture of aircrafts and tools. Reasons: The alloys are light, corrosion resistant and have high structural strength . vi) Thermite Welding: The Thermite process is used for welding of the broken ends of a girder. Reason: Aluminium is a strong reducing agent. It reduces oxides of less reactive metals like iron and chromium to the respective metals. Principle: The reduction of metal oxides with aluminum powder are accompanied by the release of huge amount of energy . This reaction is called Thermite or Aluminothermy process. Procedure: Thermite process is very useful for the welding of broken metal parts. When aluminum powder reacts with iron oxide or chromium oxide, a large amount of heat is released and about a temperature of 3500oC is attained which is enough to weld broken metallic parts. Aluminium reduces the oxide of iron or chromium to form iron or chromium metal and itself becomes aluminium oxide. The Thermite mixture is Al + Fe2O3. A burning Magnesium ribbon serves to ignite the thermite mixture. The reaction is highly exothermic; an enormous amount of heat energy is evolved. The reduced molten iron sinks and flows into the gap of the girder , thereby the welding occurs. 2Al + Fe2O3 2Al + Cr2O3 Al2O3 + 2Fe + Al2O3+ 2Cr + Uses of Zinc: i) Galvanization: Definition: Galvanization is the process of coating iron with zinc to prevent the iron from rusting. Uses: Galvanised iron ( G.I ) is used to make buckets, roofs and pipes. Reason: Zinc is used in the galvanization of iron due to the following reasons: Zinc is placed above iron in the electrochemical series ie. Zinc is more electropositive than iron Zinc ionizes ( to form Zn2+ ions) more readily than iron. Procedure: Hot iron sheets are dipped into molten zinc and passed through rollers above 300 C. Thus zinc forms a protective layer over zinc. Electro galvanizing can also be carried out. Disadvantages of G.I : Galvanized iron cannot be used to store food because zinc is poisonous. ii) Dry Cells: Zinc acts as the negative terminal in the Dry cell. Reason: Zinc acts as a negative electrode because: Zinc is highly electropositive , Zinc easily ionizes to form Zn2+ ions iii) Alloys : The important alloys of zinc are Brass and Bronze. Reason: Zinc imparts hardness to the base metal copper in these alloys. iv) Cosmetics and medicines: Zinc dust is used in the manufacture of perfumes and in pharmaceutical preparations. Reason: Zinc dust is a reducing agent. Zinc – copper couple is used as a reducing agent in organic chemistry. Uses of Iron: After aluminium, iron is the most abundant metal found on Earth’s crust. It has a very wide range of uses in its various forms. The various forms of iron, their composition and uses are listed below in the following table: Form of Iron i) Pig iron / Cast iron. Pig iron is easily cast and expands on solidification ii) Wrought iron Carbon content 2.5 – 5% Properties Uses Brittle, Non- Malleable, Non- ductile, Cannot be tempered or welded. Used in drain pipes, gutter covers and weights 0.1 – 0.25 % Non- Brittle, Malleable, Ductile, Can Used in chains, anchors, be tempered and welded, Can horseshoes and withstand strain. electromagnets. iii) Steel 0.1 –1.5% Brittle , Hard, Malleable, Ductile ,Can Used in ships, automobiles, be tempered and welded, Has high machines structural strength and tensile strength iv) Mild steel 0.1 – 0.5% Malleable, Ductile Used in nuts and bolts v) Hard steel 0.5 – 1.5% Hard, Brittle Used in tools There are different types of steel depending on its hardness, brittleness and tensile strength. modify the properties of steel, different types of heat treatment are given to steel namely Hardening ( Quenching) and Annealing (Tempering). Hardening ( Quenching) Manufacture: Hard steel is heated to red hot above 800oC and plunged into cold water or oil. . Annealing (Tempering) Manufacture: Hard steel is heated to temperatures between 220oC and 300 oC and cooled slowly for 4 -5 hours. Property modifications: Increase in hardness, Increase in brittleness Property modifications: Retains hardness and Brittleness, Increase in tensile strength Uses: Specific machine parts. Uses: Razor blades and Springs. Rusting of iron ( Corrosion of iron) and Prevention: Rusting is the process of oxidation of iron when iron is exposed to moisture and air to give a reddish brown coating of hydrated iron ( III ) oxide. Chemically, rust is hydrated iron ( III ) oxide. moisture 4Fe + 3O2 + x H2O 2Fe2O3 .xH2O ( Hydrated iron (III) oxide or rust ) Two essential conditions for the rusting of iron: i) Moisture ii) Air / oxygen Prevention of rusting of iron: The methods involve the prevention of both moisture and oxygen from coming in contact with iron objects. Painting: Red lead oxide paint is applied on the heavy iron parts in vehicles, machinery etc. Aluminium paint is applied on telegraph poles and it acts as an anti corrosive paint. Galvanizing: Iron sheets are dipped in molten zinc and used to make buckets, roofs, pipes etc., Experiment to demonstrate that both moisture and oxygen are necessary for rusting: Test tube A: The polished iron nails get rusted since both moisture ( from tap water) and oxygen are present. Test tube B : The polished iron nails do not get rusted since boiling removes the oxygen dissolved in wate and the layer of oil cuts off the oxygen from air. The test tube is sealed.Hence even though moisture is present, the nails do not rust due to the absence of oxygen. Test tube C: The polished iron nails do not get rusted . The anhydrous calcium chloride acts as a drying agent and absorbs moisture from the air inside the test tube . Hence even though oxygen is present, the nails do not rust due to the absence of moisture. This experiment proves that both moisture and oxygen are required for rusting. Alloys: An alloy is a homogeneous mixture of two or more metals mixed in definite proportions so as to obtain desired properties. It is usually prepared by melting the components together and solidifying the mixture. So the components must be miscible in liquid state and should not separate on solidification. The properties of the alloy are intermediate between those of the constituent metals. The metal present in the larger proportion in the alloy is called the base metal. Eg. In brass, the base metal is copper. If the base metal is mercury , the alloy is termed as amalgam.eg: Na /Hg amalgam. List of some important alloys, their composition and uses: Name of alloy i) Brass ii) Bronze Composition Cu ( 60 -80% ), Zn ( 40 -20% ) Base metal Copper iii) Duralumin Cu (80% ), Sn ( 19% ), Zn (1%) Al (95%), Cu (4%), Mg(0.45%), Mn(0.5%) iv) Solder (Fuse metal) Pb ( 50 % ), Sn (50 %) _______ v) Stainless steel Fe (75%), Ni (10%), Cr(15%), C (0.5%) Iron Copper Aluminium Properties Uses Hard , lustrous, easily cast, malleable and ductile Hard, attractive ,takes up polish Electrical fittings , Medals Stronger than Al . Aluminium imparts lightness while Mg imparts strength The melting point of the alloy( 180oC ) is lower than Sn and Pb. The melting point is lowered and the alloy has high tensile strength. Ni, Cr – imparts lustre, Cr- prevents corrosion, C- imparts hardness Statues, medals , coins Aircrafts, light tools, cooker, ships Electrical fuse, Electrical welding and soldering Utensils, cutlery, automobiles vi) Nickel steel Fe (97%), Ni (2%), C (1%) Iron Elastic . Ni imparts high tensile strength Cables, aircraft parts Some other alloys: Name of alloy Composition i)German silver Cu and Zn Base metal Cu ii) Gun metal Cu, Zn, Sn, Pb Cu iii) Bell metal iv) Magnalium Cu, Sn Al, Mg Cu Al v) Type metal Pb, Sn, Sb Pb Topic: Properties Uses Hard, silvery, takes up polish a Zn Hard, brittle, easily cast Decorative articles Brittle, sonorous Light, tough, corrosion resistant Low m.p, easily cast, expands easily on solidification Metallurgy – Part 3 Terms used in Metallurgy: Metallurgy: Mineral: Ore: Matrix or Gangue: Flux: Eg: In the extraction of iron from iron ore, Some common ores of iron, zinc and aluminium: Barrels, cannons, bearings Bells, Gongs Aircraft, scientific tools Printing blocks Ores of Aluminium: Chemical Formula Common name Chemical name Chemical Formula Ores of Zinc: Common name Chemical name Chemical Formula Ores of Iron: Common name Chemical name Chemical Formula Some metals like Au and Pt occur native (free or uncombined state) Steps involved in metallurgical operations: Step I: Step II : Step III: Step IV: Concentration of the Ore (Ore dressing) Conversion of ore to oxide(Roasting or Calcination ) Reduction of metallic oxide to metal Refining of impure metal to get pure metal Step I : Concentration of the ore or ore dressing: The following methods may be used for concentration of ores: i) Magnetic separation: Principle: Used to separate eg: OR eg: Process: Diagram : ii) Froth Floatation: Used for the concentration of _______________________ores like __________________________________________. Principle: Process: Diagram: iii) Hydrolytic Method or Gravity Separation: Principle: Process: Diagram: iv) Chemical method: Addition of a chemical substance. Eg: Addition of conc. NaOH solution in the Bayer’s process used in the concentration of bauxite ore during the extraction of aluminium. Step II: Concentration of ore to oxide since oxides are easily reduced. This step is not needed if the ore is an oxide. There are two methods to convert non- oxide ores to oxides : Roasting and Calcination. Roasting: eg: i) ii) Calcination: eg: i) ii) Distinguish between Roasting and Calcination: Roasting 1. 1. 2. 2. 3. 3. Calcination Step III: Reduction of oxides of metals to the metals – Most important step in metallurgy The three main methods used for reduction of oxide ores to the respective metals are: Electrolytic reduction : involves extraction of the metal by the electrolysis of fused salts like chlorides, oxides etc., Chemical reduction : involves extraction of the metal by the reduction of metallic oxides using common reducing agents like coke, carbon monoxide, hydrogen etc., Thermal reduction : By the thermal decomposition of the oxides of metals which are unstable to heat like the oxides of silver and mercury The method selected for the reduction of the oxide depends on the position of the metal in the Metal Activity series: Activity series Characteristics of metal and its Method of extraction and equations ore K Metals Method: eg 1) Metallic ores eg 2) Al Zn Metals Method: eg i) ii) Metallic ores H iii) Cu iv) Before the reduction, the ores are converted to oxides since oxides are easily reduced. Sulphide ores are roasted : Equation: Carbonate ores are calcined: Equation: Once the oxide ores are obtained, they are then subjected to chemical reduction. Hg Metals Method: eg i) Ag Metallic ores eg 2) Step IV: Refining of impure metal obtained after reduction to get pure metal The following methods may be used: Distillation refining: Used for Principle: Liquation refining: Used for Principle : Oxidation refining: Used for Principle: Electrolytic refining: Used for Principle: Metallurgy – part 4 : Extraction of aluminium from Bauxite Aluminium is the most abundant metal on the Earth’s surface. The important ores of aluminium are bauxite , cryolite and corundum. Generally, aluminium is extracted from bauxite ore ( Al2O3.2H2O ) Steps involved in the extraction of aluminium from Bauxite: Step 1: Step 2: Step 3: Step 4: Step 1: Concentration of bauxite ore or Ore dressing: Chemical method (Bayer’s process) In this step, impure bauxite ( Al2O3.2H2O ) is converted to pure alumina ( Al2O3) Conversion of impure bauxite to sodium aluminate: Reagent added: Procedure: Principle: Equation: Conversion of sodium aluminate to aluminium hydroxide: Equation: Procedure: Conversion of aluminium hydroxide to pure alumina: Equation: Procedure: Step 2: Roasting or Calcination not required for oxide ore Step 2: Electrolytic reduction of pure alumina (Al2O3 ) : Hall Heroult’s process Electrolyte: Electrolytic Cell: Electrodes (inert) : Cathode: Anode: Temperature: Current: Electrolytic reactions: Ionisation: Cathode: Reason: Anode: Products: Diagram: Hall Heroult's process Why is electrolysis used for the reduction of alumina? What were the difficulties encountered during the reduction of alumina ? Why are fused cryolite and fluorspar added to the electrolytic mixture? Why is a layer of coke sprinkled over the electrolytic mixture? Why should the graphite anodes be continuously replaced during the electrolysis? How is the metal removed? Which arrangement indicates that it is time to add more electrolyte? Aluminum obtained by Hall Heroult’s process is 99.5% pure and has to be refined electrolytically. Step 4: Refining of impure Al to obtain pure Al by electrorefining ( Hoope’s process) 3 layers in the electrolytic tank: Upper layer: Middle layer: Lower layer: Diagram: Hoope's process Electrolytic reactions: Cathode: Anode: Collection: Extraction of Zinc: 1. Concentration of ore: By___________________ 2. Roasting: 3. Reduction: 4. Refining of zinc spelter to get pure zinc: Calcination: Extraction of iron from haematite: 1. Concentration of ore : 2. Reduction: Reducing agent: Flux : 3 zones in the Blast furnace: Pig iron: Conversion of pig iron to steel: _________________________________________