REVIEW QUESTIONS Chapter The alcohol in gasohol burns according to the equation shown below: 1 mol

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1 Chemistry 101 ANSWER KEY REVIEW QUESTIONS Chapter 4 1. The alcohol in gasohol burns according to the equation shown below: CH5OH (l) + O (g) CO (g) + HO l) How many grams of CO are produced when.00 g of CH5OH burns according to this reaction? (Assume ecess oygen).00 g CH5OH CO g 1 C H OH g = 5.7 g CO. Ammonia burns in air according to the reaction shown below: 4 NH (g) + 5 O (g) 4 NO (g) + 6 HO (l) a) How many grams of NO form when 1.50 g NH react with 1.85 g of O react with one another g NH 4 NO g 4 NH 0.01 g =.64 g NO 1.85 g O 4 NO.00 g 5 O 0.01 g = 1.9 g NO LR (correct answer) b) After the reaction above has completed, which reactant, and how much of it remains unreacted? 1.85 g O.00 g 4 mol NH 5 mol O Ecess NH = 1.50 g g = 0.71 g g = g NH 1

2 . When 0.0 g of benzene (C6H6) and 65.0 g of bromine are reacted together as shown below, 56.7 g of bromobenzene (C6H5Br) is formed. What is the percent yield of this reaction? 0.0 g C6H g Br 78.1 g g C6H6 + Br C6H5Br + HBr C H Br g = 60. g C6H5Br Theoretical Yield C H C H Br g = 6.9 g C6H5Br Br 56.7 % Yield = 100 = 94.0% 60. g 4. How many grams of solute are present in 50.0 ml of 1. M CuSO4 solution? 50.0 ml 10 ml 1. mol CuSO g = 10.6 g CuSO 4 5. How many ml of 1.50 M NaPO4 solution contains 5.00 g of solute? 5.00 g g 10 ml = 0. ml 1.50 mol 6. What volume of 1.50 M solution of sucrose solution is required to prepare 45 ml of M solution? M V 1 1 V = = M (0.100 M )(45 ml) 1.50 M = 8. ml

3 7. Glacial acetic acid has a density of g/ml at 5 C. What is the molarity of a solution of acetic acid prepared by dissolving ml of glacial acetic acid at 5 C in enough water to make ml of solution? ml g 1 ml 1 =1.747 M g L 8. The acetylsalicylic content of aspirin can be determined by reaction of the acid with sodium hydroide as shown below: HC9H7O4 + NaOH NaC9H7O4 + HO acetylsalicylic acid.0 ml of M NaOH solution was used to completely react with the acid present in a 500mg aspirin tablet. What is the percent of acetylsalicylic acid in the aspirin tablet? mol.0 ml NaOH 10 ml HC H O NaOH g 10 mg = 19 mg HC9H7O4 1 g 19 mg % Acid = 100 = 6.8% 500 mg 9. Concentrated nitric acid has a density of 1.41 g/ml and contains 70.0% HNO by mass. What is the molarity of this solution? Assume 1.00 L of solution 1.00 L sol'n 10 ml 1.41 g 1 ml 70.0 g acid 100 g sol'n = 15.7 mol HNO 6.0 g molarity = 15.7 mol = 15.7 M

4 10. How many grams of Na must react with 155 ml of water to produce a solution that is M NaOH, as shown below. (Assume a final solution volume of 155 ml) Na (s) + HO (l) NaOH (aq) + H (g) 155 ml 10 ml mol NaOH mol Na.99 g = 0.64 g Na mol NaOH 11. A sample of limestone (containing CaCO) weighing 48 mg is treated with oalic acid (HCO4), as shown below: CaCO (s) + HCO4 (aq) CaCO4 (s) + HO (l) + CO (g) The mass of CaCO4 produced in this reaction was found to be 47 mg. Based on this information, what is the mass percent of calcium carbonate in limestone? 47 mg CaCO4 1 g 10 mg CaCO g CaC O 69 mg % = 100 = 84.% 48 mg g 10 mg = 0.69 g CaCO 1 g 4

5 1. Identify each of the following substances as a nonelectrolyte (NE), weak electrolyte (WE), or strong electrolyte (SE): a) HF WE b) CH5OH NE c) LiOH SE d) HClO SE e) Cu(NO) SE f) HPO4 WE 1. Complete each equation shown below: HO a) AlCl (s) Al + (aq) + Cl (aq) HO b) NaPO4 (s) Na + (aq) + PO4 (aq) HO c) (NH4)CO (s) NH4 + (aq) + CO (aq) 14. Complete the molecular equations shown below, and write balanced net ionic equations for each: a) Pb(NO) (aq) + NaSO4 (aq) PbSO4 (s) + NaNO (aq) Pb + (aq) + SO4 (aq) PbSO4 (s) b) Cr(OH) (aq) + HNO (aq) Cr(NO) (aq) + HO (l) Cr(OH) (aq) + H + Cr + + HO (l) Note: Cr(OH) is a weak base and therefore should be represented as a molecule. 5

6 15. For each reaction shown below, determine if a reaction occurs. If so, write a balanced net ionic equation. If not, write No Rn. a) Ca(OH) (aq) + HCN (aq) Ca(CN) (aq) + HO (l) OH (aq) + HCN (aq) CN (aq) + HO b) AgNO (aq) + NaCO (aq) AgCO (s) + NaNO (aq) Ag + (aq) + CO AgCO (s) c) NaCl (aq) + (NH4)SO4 (aq) No Rn d) NaPO4 (aq) + HBr (aq) HPO4 (aq) + NaBr (aq) PO4 (aq) + H + HPO4 (aq) 16. Write balanced net ionic equations for each reaction described below: a) Solid sodium hydroide pellets are dropped in solution of sulfuric acid. NaOH (s) + HSO4 (aq) NaSO4 (aq) + HO (l) NaOH (s) + H + (aq) Na + (aq) + HO (l) b) Aqueous solutions of ammonium carbonate and calcium chloride are mied together. (NH4)CO (aq) + CaCl (aq) CaCO (s) + NH4Cl (aq) CO + Ca + CaCO (s) 6

7 17. In the compounds below, assign oidation numbers to the underlined element: a) HPO +1 d) HCO 0 b) NaCO4 + e) ClF4 + c) MnSO4 +6 g) AlH Identify which substance is oidized and which substance is reduced in each of the following redo reactions a) Al + Cl AlCl oidized Al reduced Cl 0 +4 b) NiS + O NiO + SO oidized S reduced O c) HS + HNO S + NO + 4 HO Oidized S reduced N 19. A solution is prepared by miing 0.10 L of 0.1 M NaCl and 0. L of 0.18 M MgCl solutions. What volume of 0.5 M AgNO is required to precipitate all the chloride ions in the solution above? (Answer = 0.8 L) AgNO (aq) + Cl (aq) AgCl (s) + NO (aq) 0.1 mol Cl 0.10 L NaCl = 0.01 mol Cl NaCl 0.18 mol mol Cl 0. L MgCl = mol Cl MgCl Total mol of Cl = = mol mol Cl AgNO = 0.8 L Cl 0.5 mol 7

8 0. When B5H9 reacts with water, it forms boric acid (HBO) and hydrogen gas. Boric acid combines with sodium oide to form borate salt NaB4O7 and water. What mass of B5H9 is required to form 151 g of the borate salt by this reaction sequence? (Answer = 7.9 g) 4 (B5H HO 5 HBO + 1 H ) 5 ( 4 HBO Na O Na B O + 6 H O) 4 B H + 5 Na O + 0 H O 5 Na B O + 48 H g Na B O g 4 mol B H 6.14 g = 7.9 g B5H9 5 mol Na B O Balance each oidation or reduction halfreaction shown below: a) _1_ MnO4 + HO + e _1_MnO + _4_OH b) 1_HO + 1 HSO 1_SO4 + H + + e +4 + c) HO 1 NiO + e 1_Ni(OH) + OH d) H ClO + 1e 1_ClO + 1_HO. What is the overall equation formed from combining halfreactions (b) and (d) above? HO + HSO SO4 + H + + e ( H + + ClO + 1e ClO + HO) Combining the equations above and cancelling electrons, H + and HO, results the following overall equation: H + + HSO + ClO SO4 + ClO + HO 8

9 . A person s blood alcohol (CH5OH) can be determined by titrating a sample of blood plasma with a sodium dichromate solution. The balanced equation is: 16 H + (aq) + CrO7 (aq) + CH5OH (aq) 4 Cr + (aq) + CO (g) + 11 HO (l) If 5.46 ml of M CrO7 is required to titrate 5.00 g of plasma, what is the mass percent of alcohol in blood? (Answer = 0.161%) 5.46 ml CrO CH5OH g = g C 10 ml mol Cr O H5OH g C H OH 5.00 g blood 5 % CH5OH 100 = 0.161% 7 4. Phosphoric acid can be produced by reaction of aqueous sodium phosphate and sulfuric acid. The other product in the reaction is sodium sulfate. a) What volume (in ml) of 1.55 M sulfuric acid is required to completely react with 7.5 ml of 1.0 M sodium phosphate? Na PO (aq) + H SO (aq) H PO (aq) + Na SO (aq) ml NaPO 4 10 ml 1.0 mol mol HSO4 10 ml = 1.9 ml mol Na PO mol b) What is the concentration of the phosphoric acid produced in the final solution? 1.0 mol mol HPO4 7.5 ml NaPO 4 = 0.00 mol H PO 10 ml mol NaPO 4 Total volume of solution = 7.5 ml ml = 59.4 ml = L 0.00 mol Molarity of HPO 4 = = M L 4 9