2014 END TERM 2 CHEMISTRY FORM 3 - KCPE-KCSE
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NAME…………………………………………………….………..ADM NO…………CLASS……… KCSE ONLINE EXAMS CHEMISTRY 233 (1, 2, AND 3 Combined) July/August 2014 28th July 2014 FORM THREE CHEMISTRY AFRAHA HIGH SCHOOL TIME: 2 HOURS INSTRUCTIONS ο· Answer All the Questions in the spaces provided. ο· All workings must be clearly shown ο· Mathematical tables and electronic calculators may be used. 1. Hexanol (CH3CH2CH2CH2CH2CH2OH) has a melting point of -520C and a boiling point of 1570C. a) Identify the different elements that constitute hexanol. (3mks) …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… b) Determine the number of atoms present in one molecule of hexanol. (1mk) c) What is the physical state of hexanol at room temperature? (1mk) …………………………………………………………………………………………………………… 2. The diagram below summarises the change that water undergoes on heating followed by cooling. Study it and answer the questions that follow. A N -400C Q B 500C P R C 1200C a) Name the physical stated represented by letter A, B, C. (3mks) A _____________________________________________________ B ______________________________________________________ C ______________________________________________________ 1 b) Name the processes represented by the letters N, P, Q and R. N ________________________________________________________ (4mks) P _________________________________________________________ Q ________________________________________________________ R _______________________________________________________ c) Name the changes above that; i) Absorb heat in order to occur. (2mks) …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… ii) Release heat when they occur. (2 mks) …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… 3. a) Name the most suitable agents for removing the following stains from your school uniform; i) Oil and grease _____________________________________________________________ (1mk) ii) Blood stains _____________________________________________________________ (1mk) b) Which method of separation is utilized in the above procedure? (1mk) …………………………………………………………………………………………………………… 4. Write balanced chemical equations for the following reactions. (5mks) a) Strongly heating copper (II) nitrate it decompose to copper (II) oxide, nitrogen (IV)oxide and oxygen. …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… b) Placing sodium metal in water forming sodium hydroxide and hydrogen gas. …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… c) Strongly heating copper meta in air to form copper (II) oxide. …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… d) Hydrogen gas combining with oxygen to form water. …………………………………………………………………………………………………………… e) Burning charcoal in excess air to form carbon (IV) oxide 2 …………………………………………………………………………………………………………… 5. Oxygen can be prepared by decomposition of hydrogen peroxide using manganese (IV) oxide as a catalyst. The gas is collected over water in a glass trough. a) Draw the arrangement of the apparatus showing how oxygen is prepared and collected. (5mks) b) What makes it possible for oxygen to be collected over water? (1mk) …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… c) What happens when a burning magnesium ribbon is introduced in gas jar full of; i) Oxygen (1mk) …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… ii) Carbon (IV) oxide gas. (1mk) …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… d) Write a balanced equation for the decomposition of hydrogen peroxide (H2O2) (2mks) 3 …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… e) List three uses oxygen. (3mks) …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… 6. a) What are Isotopes? (3mks) …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… b) Determine the relative atomic mass of Potassium whose isotopic mixture occurs in the proportions shown below. (3mks) Potassium – 39 Potassium - 40 Potassium – 41 93.1% 0.01% 6.89% c) Determine the number of neutrons in the following elements (4mks) i) 147N ii) 35 17Cl iii) 37 17πΆπ 4 iv) 23 11Na 7. Use Lewis dot(.) and cross (x) diagrams to show bonding in each of the following compounds. (6mks) a) Magnesium chloride (Mg=12, Cl=17) b) Carbon tetrachloride (C=6, Cl=17) c) Water (H=1, O=8) 8. a) State Boyle’s Law. (1mk) 5 …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… b) A certain mass of a gas occupies a volume of 290dm3 at 720C and 900mmHg. At what temperature in 0C will the volume be 190dm3 at 1200mmHg pressure? (3mks) 9. A 21g sample of a compound was found to contain 6g magnesium 3g carbon and the rest is oxygen. Determine its empirical formula (Mg=24, C=12, O=16). (3mks) 10. In a titration experiment, a study was provided with the following reagents; ο· ο· Solution P which is 0.187M HCl Solution Q which contains 2.65g of metal carbonate X2CO3 in 250cm3 solution. He titrated 25cm3 of X2CO3 with the HCl solution and obtained the following results. Titration Final burette reading 26.75 27.20 36.65 Initial burette reading 0.0 0.5 10.0 Colume of HCl used in cm3 a) Complete the table. (1mk) 6 b) If methyl orange was used as the indicator, what colour change would you expect? (1mk) …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… c) Calculate the average volume of P used. (1mk) d) Write a balanced equation for the reaction that took place. (1mk) e) Calculate the number of moles of the acid used. (2mks) f) Calculate the number of moles of the carbonate used. (2mks) g) Determine the molarity of the carbonate. (2mks) h) Determine the molar mass of X2CO3. (2mks) i) Determine the value of X. (2mks) 7 11. a) Use the IUPAC system of nomenclature to name the following compounds. i) CH3CH2CH3 (5mks) ________________________________________________________________________________ ii) CH2CHCH2CH3 _______________________________________________________________________________ iii) CHCCH2CH3 ________________________________________________________________________________ H H iv) CH3 - C - C – CH2 CH3 __________________________________________________________________________________ CH3 B v) CH3 CH3 - H C - C - CH3 CH3 _______________________________________________________________________________________ CH3 B) The reaction scheme below shows a series of reactions starting with ethanol. Sud it and answer the questions that follow. Ethanol Ch3Ch2OH KmnO4 H+ CH3Coo H Step I CH2=CH2 NaOH aq CH3CooNG Step W Step II CH3CH3 CH4 Excess Cl2 UV light Compound X Compound K -CH2-CH2 - n i) For each of the steps labeled I and II, give the type of reaction, the reagent(s) and/or catalyst and the condition(s) necessary for it to take place (6mks) 8 Step Type of Reaction I II Reagent(s) and/or catalyst(s) Condition(s) ii) State the reagent(s) and condition(s) necessary for step W to take place. (2mks) Reagent (s) ________________________________________________________________________ Condition(s) ______________________________________________________________________ iii) Name compound K and state the type of reaction involved in its formation. (2mks) Name…………………………………………………………………………………………………… Type of reaction…………………………..…………………………………………………………… iv) Give the name and structure formula of compound X. (2mks) Name…………………………………………………………………………………………………… Formula of ……………………………………………………………………………………………… v) If the relative molecular mass of K is 22400, determine the value of n. (C=12, H=1) (2mks) 12. The flowchart below represents the industrial preparation of nitric acid. Study it and answer the questions that follow. 9 a) State what happens in the heat exchanger. (1mk) …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… b) Write an equation for the reaction that takes place in the catalyst chamber and name the catalyst. (2mks) Equation __________________________________________________________________________________ Catalyst ______________________________________________________________________ c) Name the gases in mixture R that are important for the subsequent steps. (2mks) …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… d) State what happens in chamber Y. (1mk) …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… e) Give the equation for the overall reaction that takes place in chamber Z. (2mks) …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… f) How is the operating temperature in this process maintained? (1mk) …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… g) The final product form this process contains 60-65% nitric acid. How is the concentration of nitric acid increased? (1mk) …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… h) Why is the manufactured nitric acid stored in dark bottles? (1mk) …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… i) List down three uses of nitric acid. (3mks) 10 …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… 13. a) Which is a richer source of nitrogen, urea (NH2)2CO or Ammonium phosphate (NH4)3PO4? Show your working. (N=14, H=1, C=12, O=16, P=31) (4mks) b) Name 3 oxides of nitrogen. (3mks) …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… …………………………………………………………………………………………………………… 11
