Analytical Chemistry (MODULE 1) Whether inorganic or organic has to be investigated systematically using wellorganized methods where meticulous observations are done so that logical conclusion is made accurately. Uses instruments to separate, identify and quantify matter precise measurements are usually needed to determine its exact composition. Aims to determine what elements, ions, functional groups, or compounds are present in a given sample. Analytical chemists in industry: Lawyers, Other chemists, Colleges universities, Health and safety, Production plants, Contract labs, Management, Professional organizations, Statisticians, Government agencies, Engineers, Suppliers, Sales and marketing, Life scientists, Technical reps in field, Peers, supervisors, Forensic chemists. (In 1997, the quest for information from the planet Mars by the Pathfinder spacecraft used qualitative analysis to determine what compounds or elements were in the rock samples.) Quantitative analysis: know how much of the compound, ions, or elements confirmed present by qualitative analysis is actually present. Determines numerical amount or concentration hundred(percentage), parts per million (ppm) or part per billion(ppb) (uses mass or volume) Qualitative analysis: Identifies analytes (substances) Separation-isolates analytes (substances) i.e. precipitation, extraction, distillation Identification of substance: may be based on color, odor, melting point, boiling point, and radioactivity/reactivity. Sampling techniques Analytical chemists utilize coning and quartering to decrease the sample size of a powder without producing systematic bias. Coning involves putting the sample into a conical shape and then, Quarteringflattening it into a cake-like or disk shape that is then divided into 4 quadrants. The 2-opposite quadrant are combined forming another cone and then quartered again. This process will continue until the sample will reduce small enough to fit for laboratory sample. Then the sample will be dissolved in water that we can call Aliquot- the exact divisor or factor of a quantity. Basic chemistry principles Chemical reactions- conversion of natural substances into new compounds with different and sometimes superior properties. breaking bond in the reactants (starting materials) Forming new bonds in the product Involves to metabolism of food, as well. Law of mass conservation The total mass of substances does not change during a chemical reaction “atoms cannot be created or destroyed.” Law of definite composition No matter what the source, a particular compound is composed of the same elements in the same parts (fractions) by mass. “every chemical compound contains fixed and constant proportions.” Law of multiple proportion If element A and B react to form two compounds, the different masses of B that combine with a fixed mass of A can be expressed as a ratio of small whole numbers. “When two elements combine to generate more than one compound, the weights of one element mix with a fixed weight of the other in a tiny whole number ratio.” △ (s) (l) (g) Balancing equation terms: Read as “yields” Reaction occurs Heat Solid Liquid Gas Number beside a letter Set slightly below or above the normal line Substance that takes part in and undergoes Reactant change during a reaction. Substance that is formed as the result of a Product chemical reaction. Chemical equation- chemist’s shorthand descriptions Steps in balancing chemical equation Coefficient Subscripts Step1 Write the equation with the correct formulas. Step2 Balance the equation with coefficients one element at a time. Step3 Check to make sure that the smallest set of whole numbers is used. Redox reaction - Addition of oxygen - Increase in valence/oxidation number - Loss of electron or hydrogen - Substances oxidized - Reducing agent VILEORA -Valence of an element Increases that means it Lost Electron, it was Oxidized and its compound acts as the Reducing Agent. Reduction reaction - Addition of hydrogen - Decrease in valence/ oxidation number - Gain of electron or hydrogen - Substance reduced - Oxidizing agent VDGEROA- Valence of an element Decreases that means it Gained Electrons, it was Reduced and its compound is the Oxidizing Agent. Module 1 Activities: M1 Pre-Task Take a look at the nutrition facts on your favorite snack. Note also the content of each multi-vitamin tablet. What appears on the label is from the tedious analysis of analytical chemists. Have pictures of these (one each) and upload them in the reply box. M1 Activity 1 After studying the lesson and watching the videos, answer the following questions in the reply box. The answer must not exceed 5 sentences per question. 1. What problems of society can analytical chemists help in finding solutions? How do they do it? In forensic science, investigators are able to detect illegal compounds from suspected drug users using analytical chemistry. In breath biopsy, chemical analysts recognize valuable information about a disease like asthma, or any infectious disease. Chemistry is truly majestic in its own right. Another advantage of chemistry is that it helps with our problem of plastic pollution and environmental monitoring. Analytical chemistry is also used in food production, which we may not be aware of, but the nutritional facts of our food are from the analysis of an analytical chemist. 2. Discuss the quartering method of sampling. First, a sample must shape into conical/ cone form and then, Quartering- flattening it into a cake-like or disk shape that is then divided into 4 quadrants. The 2opposite quadrant are combined forming another cone and then quartered again. This process will continue until the sample will reduce small enough to fit for laboratory sample. Then the sample will be dissolved in water that we can call Aliquot- the exact divisor or factor of a quantity. This is utilized by the chemists in order to decrease a sample size that can fit in the laboratory. M1 Activity 2 After studying the lesson and the PowerPoint presentations, please answer the following questions. Use one whole sheet intermediate pad paper folded lengthwise. Write legibly and no erasures. For numbers 6-8, show your solution, encircle final answer and final answer must have correct number of significant figures. 1. Write a complete balanced chemical equation for the decomposition of solid potassium chlorate upon heating. 2KClO3 (s) → 2KCl(s) + 3O2 2. Balance and translate the given chemical equation to a word equation. BaCl2(aq) + Na2SO4(aq) → BaSO4(s) + 2NaCl(aq) Barium chloride reacts with sodium sulphate to produce insoluble barium sulphate (precipitate) and sodium chloride solution 3. Three moles of sulphuric acid react with two moles of aluminium metal to give one mole of aluminium sulphate and three moles of hydrogen gas. Write the balanced chemical equation corresponding to this reaction. 3(H2SO4) (aq) + 2Al Al2 (SO4)3(aq) +3H2 (g) 4. Balance the given equation using the valence change method. Identify the reducing agent and the oxidizing agent. H2S + H2O2 → S + H2O H2 -1S-2 (g) + H2 -2O2-1 (aq) → S0 (s) + 2 H2 -1O-2 (l) H2S is a reducing agent, H2O2 is an oxidizing agent. S-II - 2 e- → S0 (oxidation) 2 O-I + 2 e- → 2 O-II (reduction) 5. Balance the given equation using the half-reaction method. Identify the ion or element that gained electron and indicate the number of electrons gained. Identify the ion or element that lost electron and indicate the number of electrons lost. Fe2+ + Cl2 → Fe3+ + ClFe2+ + Cl2 → Fe3+ + 2ClFe2+ Fe3++ee-Cl20 2Cl-1 -- Fe2+ Fe2+ -- Cl2-1 2Cl-1 (oxidation) (Fe gained 1 electron) (reduction) (Cl lost 1 electron) 6. What is the molar mass of the following compounds. a. Epsom Salt, the chemical formula is MgSO4 . 7H2O Mg=24.305 S=32.065 O=15.9994 H=1.00794 24.305 + 32.065 + 15.9994*4 + 7*(1.00794*2 + 15.9994) Molar mass of MgSO4.7H2O = 246.47g/mol b. Ammonium phosphate (NH4)3PO4 N= 14.0067 H= 1.00784 P= 30.973762 O= 15.999 (14.0067+ 1.00784*4)3+ 30.973762+ (15.999* 4) Molar mass of (NH4)3PO4 = 149.05 g/mol 7. Aluminium reacts with iodine according to the following equation: 2Al(s) + 3I2(s) → Al2 I6(s) a. How many moles of Al2 I6 are produced by the reaction of 4.0 mole of aluminium? 4.0 mol Al2 X 1 mol Al2 I 6 1 = 2 mol Al2 I 6 2 mol Al2 b. How many moles of I2 are required to react exactly with 0.429 mole of aluminium? 0.429 A2 X 3 mol I2 1 = 0.64 mol I2 2Al2 8. Methanol (CH4O), which is used as a fuel in high –performance racing cars, burns in the presence of O2 to form CO2 and H2 2CH4O(l) + 3O2(g) → 2CO2(g) + 4H2O(g) a. What is the theoretical yield of CO2 from 48.0 grams of methanol? 48.0 g CH4O X 1 mol CH4O =1.50 mol CH4O X 2 mol CH4O = 1.50 mol CO2 X 44.0 g CO2 1 32.0 g CH4O 2 mol CH4O 2 mol CH4O = 66.0 g CO2 Theoretical yield b. What is the percent yield of CO2 if 48.0 grams of carbon dioxide are formed? Percent yield = 48.0 g CO2 X 100% = 72.7% 66.0 g CO2 Research and type the molarity of the following concentrated acids, bases, and salts using the table below. Name of Acids/Bases Concentration in Molarity (in whole numbers) Acetic Acid, Glacial 17 M Formic Acid 24 M Hydrochloric Acid 12 M Hydrofluoric Acid 29 M Nitric Acid 16 M Phosphoric Acid 15 M Sulfuric Acid 18 M Ammonium Hydroxide 15 M Potassium Hydroxide 19 M Sodium Hydroxide 12 M Reference: https://www.nestgrp.com/protocols/trng/molarity.shtml M2 Pre-Task Copy the table, write the chemical formula on the second column, and compute the molar mass on the third column. Take a picture of your paper and upload it as your assignment for this activity. CHEMICAL NAME CHEMICAL FORMULA Na2SO4 1. sodium sulfate 2. magnesium H Cl MgO6 chloride hexahydrate 12 2 3. potassium K3 [Fe(CN)6] ferricyanide 4. nitric acid HNO₃ 5. silver carbonate Ag2CO3 6. sodium NaClO hypochlorite 7. barium iodate Ba(IO3)2 8. aluminum C6Al2O12 oxalate 9. silver chromate Ag2CrO4 10. calcium Ca(OH)₂ hydroxide COMPUTATION OF MOLAR MASS COMPUTATION OF MOLAR MASS M2 Activity 1 Solve the following problems. Use intermediate pad paper. Write legibly and no erasures. Follow the given format below. Final answers must contain the correct number of significant figures. Upload your assignment as a picture. 1. Calculate the percent by mass of chromium in each of the following oxides: a. CrO3 Problem # 1.a. Given: Total molar mass of element: Cr= 51.996 O3= 15.999 (3)= 47.997 Molar mass of CrO3 = 99.99 Req’d= % mass of CrO3 =? Formula: % by mass: total molar mass of element X 100% Molar mass of whole compound Solution: % Cr= 51. 996 X100% = 52% 99.99 % O3= 47.997 X100% = 48% 99.99 (b) Cr2O3 Given: Total molar mass of element: Cr2= 51.996 (2) = 103.992 O3= 15.999 (3) = 47.997 Molar mass of Cr 2O3 = 99.99 Req’d= % mass of Cr 2O 3 =? Formula: % by mass: total molar mass of element X 100% Molar mass of whole compound Solution: % Cr2= 103.992 X100% = 68.42% 151.99 % O3= 47.997 X100% = 31.58% 151.99 2. A commercial mouthwash contains 4.3 g of ethanol and 0.021g antiseptic in each 30.-mL portion. Calculate the w/v percent concentration of each component. Given: Solutes: 4.3g of ethanol 0.021 g of antiseptic Solution: 30. mL Req’d= w/v of ethanol= ? w/v of antiseptic =? Formula: (w/v)= mass of solute (g) X100% Vol. of solution (mL) Solution: (w/v)= 4.3 (g) X100% =14% (ethanol) 0.021 (mL) (w/v)= 0.021 (g) X100% =0.070% (antiseptic) 30.(mL) 3. How many mL of ethanol are contained in a 30.-mL portion of mouthwash that has 8.0%(v/v) of ethanol? Given: Solute: ? Solution: 30. mL (v/v): 8.0% Req’d= ml of ethanol= ? Formula: (v/v)= mass of solute (g) X100% Vol. of solution (mL) Solution: 8.0%= ? mLX100% 30. mL : 8.0% = ? mL X100% 100mL 30. mL =0.08 mL X 30. mL =2.4 mL ethanol 4. A cough medicine contains 0.20% (w/v) dextromethorphan, a cough suppressant , and 2.0% (w/v) guaifenesin, an expectorant. How many mg of each drug would you obtain from 3.0 tsp of cough syrup? (1 tsp = 5 ml) Given: 0.20% (w/v) dextromethorphan 2.0% (w/v) guaifenisin 3.0 tsp = 5 mL cough syrup Req’d= ml of ethanol= ? Formula: (v/v)= mass of solute (g) X100% Vol. of solution (mL) Solution #4 5 mL cough syrup X 0.20% g dextromethorphan X dextromethorphan 100 mL cough syrup 1000 mg = 25.0 mg 1g 5 mL cough syrup X 2.0 g guaifenesin X 1000 mg = 10 mg guaifenesin 100 mL cough syrup 1g M2 Activity 3 A. Write a balanced chemical equation, total ionic equation and net ionic equation for the given pairs of salt solutions when they are mixed. 1. Pb(NO3)2 + K2SO4 → Balanced chemical equation: Pb(NO3)2 (aq) + K2SO4 (aq) → PbSO4 (s) + 2 KNO3 (aq) Ionic equation: Pb 2++ 2NO3 - (aq) + 2K +SO4 2- (aq) → PbSO4 (s) + 2 K + + 2NO3- (aq) Net ionic equation: Pb 2+ (aq) +SO4 2- (aq) → PbSO4 (s) 2. FeCl3 + NaOH → 1. Balanced chemical equation: FeCl3 (aq) + 3NaOH(aq) Fe(OH)3(s) + 3NaCl(aq) 2. Ionic equation: Fe 3+ 3Cl- (aq) + 3Na+ 3OH -(aq) Fe (OH)3(s) + 3Na + 3Cl -(aq) 3. Net ionic equation: Fe 3+(aq) + 3OH -(aq) Fe (OH)3(s) B. For the precipitate formed in question A, write its formula, chemical name and classification. Precipitate Formula - chemical name - classification 1. PbSO4 - lead(II) sulfate- sulfuric acid lead salt or anglesite 2. Fe (OH)3 - Iron(III) oxide-hydroxide- transition element molecular entity and a metallic base. Apparatus/ Equipment How You Used It Before Correct Technique in Using It Crucible I completely fill it. Fill the crucible only halfway or two-thirds full of sample chemicals; do not fill it all the way to the top. Evaporating dish One time, I forgot to Should record the mass of the dish record the mass of the dish before measuring solution Sample vial No labeling of samples Samples should always be labeled Graduated cylinder I use it to hold water It is used for measuring a solution or any liquid sample. M1 Activity 3 1. Discuss the correct laboratory technique in using the centrifuge for qualitative analysis. Give two tips on its proper use. First, calibration of the centrifuge before testing a sample has to be prioritized. Along with the test tube samples, another tube filled with water at approximately the same level as your sample test will be put. This water-filled tube should be put exactly across from your sample in the centrifuge. Hands should not be used to slow down the centrifuge head. Allow the centrifuge head to come to rest on its own instead. 2. Explain how calcium ions are confirmed present in a solid salt by using flame test. The flame test is used to visually identify an unknown metal or metalloid ion based on the salt's unique color. A few drops of dilute sodium hydroxide solution react with calcium ions to generate a white precipitate is the confirmation test. 3.Discuss a method to confirm the presence of a) phenol and b) ketone in a test compound. For the presence of phenol, make a solution of the organic compounds supplied in water, dropwise add the ferric chloride neutral solution then the color shift. The presence of phenol is indicated by the presence of red, blue, green, or purple coloration. While the presence of ketone is confirmed if there is the emergence of a red color. In a clean test tube, dissolve sodium nitroprusside in distilled water. 1ml of the organic substance to be examined is added then shake thoroughly before adding the sodium hydroxide solution dropwise. 4. How are proteins confirmed present in a sample? Explain the laboratory process. The Biuret test for proteins is used to determine the presence of protein. The Biurette reagent, which is composed of sodium hydroxide and copper (II) sulphate, aids in the detection of protein in a sample. For its procedure, add 2ml of the sodium hydroxide solution then, add 5 to 6 drops of copper sulfate solution to this. The presence of proteins is indicated by the appearance of a bluish violet color.