CHEM 102 Winter 18 Exam 3 (C) Questions and Answers,100% CORRECT

CHEM 102 Winter 18 Exam 3 (C) Questions and Answers Potentially useful data: x  2 a 1. Please choose the letter “C” as your answer for this question. 2. Consider the following endothermic chemical equilibrium. What change below would cause an increase in the I2 (g) concentration? 2 NOI (g) ⇌ 2 NO (g) + I2 (g) a) adding more NOI b) adding more NO c) decreasing the temperature d) increasing the pressure e) All of the above. 3. At 25 oC, an aqueous solution has [H3O+] = 3.1 × 10–9 M. What statement is CORRECT? a) The solution has a hydroxide ion concentration less than 1.0 × 10–7 M. b) The pH of the solution is 7.5. c) The solution does not contain any HO- ions. d) The solution has a hydronium ion concentration greater than that of a neutral solution. e) The solution is basic. 4. Which of the following chemical species is amphoteric? a) CO32- b) NH4⁺ c) HSO4- d) CH4 e) CH3COOH 5. In the chemical equilibrium below, H2CO3 + F – HCO3– + HF a) F –and HCO3– are Brønsted-Lowry bases. b) F – is a Brønsted-Lowry base and H2CO3 is a Brønsted-Lowry acid. c) H2CO3 is a base and HCO3– is its conjugate acid. d) H2CO3 is an acid and F – is its conjugate base. e) both a) and b) 6. Estimate the Kb for CN⁻ at 25 °C. The Ka for HCN is 4.9 × 10-10. -5 a) 1.4 × 10 -14 b) 4.9 × 10 -9 c) 2.3 × 10 -5 d) 2.0 × 10 -7 e) 3.7 × 10 7. An amount of 23.7 g of CaCl2 is dissolved in 375 g of water. The concentration of CaCl2 in the resulting solution is % by mass. a) 6.32 b) 5.94 c) 6.32 × 10-2 d) 5.94 × 10-2 e) 6.24 8. Which statement about the following equilibrium is CORRECT? (Ka =1.26 × 10–2 for HSO4- and Ka = 5.6 × 10–10 for NH4+) HSO4- (aq) + NH3 (aq) SO42- (aq) + NH4+ (aq) a) The equilibrium is reactant-favored because NH3 is a stronger base than SO42-. b) The initial [HSO4-] and [NH3] must be known in order to make a prediction. c) Neither reactants nor products are favored, since all species are weak acids or bases. d) The equilibrium is product-favored because HSO4- is a stronger acid than NH4+. e) No prediction can be made: the strong acid and the weak base appear on the same side of the equation. 9. Estimate the pOH of a 0.00598 M HClO4 solution at 25 oC. a) 3.56 b) 6.43 c) 7.57 d) 11.8 e) 2.22 10. Consider the following reaction: CH4 (g) + 2 H2S (g) ⇌ CS2 (g) + 4 H2 (g) Initially, the reaction mixture contained 0.50 M CH4 and 0.75 M H2S. The equilibrium concentration of H2 is 0.44 M. Estimate the equilibrium constant, Kc, for the reaction. a) 0.23 b) 10 c) 0.038 d) 0.34 e) 2.9 11. Consider the chemical equilibrium below (Kc = 0.95) and a mixture that contains 0.45 M CH3CH2OH, 0.45 M CH3COOH and 1.1 M CH3COOCH2CH3. Which of the following statements is TRUE? CH3CH2OH (aq) + CH3COOH (aq) CH3COOCH2CH3 (aq) + H2O (l) a) Q < K, so the forward reaction will proceed to form more products. b) Q < K, so the reverse reaction will proceed to form more reactants. c) Q > K, so the forward reaction will proceed to form more products. d) The reaction mixture is at equilibrium. e) Q > K, so the reverse reaction will proceed to form more reactants. 12. Estimate the volume of 0.716 M KBr(aq) that can be made from 30.5 g of pure KBr. a) 21.8 mL b) 42.7 mL c) 254 mL d) 184 mL e) 358 mL 13. In which of the following aqueous solutions does the weak acid exhibit the HIGHEST percent ionization? -4 a) 0.01 M HF (Ka =6.8 × 10 ) -2 b) 0.01 M H2SO3 (Ka =1.6 × 10 ) c) 0.01 M NH + (K =5.6 × -10 -5 d) 0.01 M CH3COOH (Ka =1.8 × 10 ) e) Since the molar concentration is the same, all given acids will exhibit the same percent ionization. 14. Identify the STRONGEST acid. a) H2Te b) H2O c) H2Se d) H2S e) Not enough information to determine. 15. Choose the TRUE statement: “A solution will form between two substances if .” a) the solute-solute interactions are strong enough to overcome the solvent-solvent interactions b) the solute-solvent interactions are weaker than the solute-solute and solvent-solvent interactions c) the solvent-solvent interactions are strong enough to overcome the solute-solvent interactions d) the solute-solvent interactions are stronger than the solute-solute and solvent-solvent interactions e) the solute-solute interactions are weaker than the solvent-solvent interactions 16. Choose the equilibrium for which an increase in pressure will shift the equilibrium to the right. a) 3 S (s) + 2 H2O (g) ⇌ 2 H2S (g) + SO2 (g) b) CO (g) + H2O (g) ⇌ CO2 (g) + H2 (g) c) 2 NO (g) + Cl2 (g) ⇌ 2 NOCl (g) d) CO2 (g) + C(graphite) ⇌ 2 CO (g) e) 2 SO3 (g) ⇌ 2 SO2 (g) + O2 (g) 17. Estimate the [H3O+] in a 0.265 M HClO solution (Ka of HClO is 2.9 × 10-8). a) 1.1 × 10-10 M b) 8.8 × 10-5 M c) 1.3 × 10-6 M d) 4.9 × 10-4 M e) 7.7 × 10-9 M 18. Consider the following reaction at equilibrium. What happens if the temperature increases? Fe3O4 (s) + CO (g) ⇌ 3 FeO (s) + CO2 (g) ΔH = +35.9 kJ a) The equilibrium will shift towards the reactants. b) The equilibrium will shift towards the least number of moles of solid. c) No effect will be observed. d) The equilibrium will shift towards the products. e) The equilibrium will shift towards the least number of moles of gas. 19. Which statement is FALSE for a strong acid? a) The conjugate base of a strong acid in water is a very small anion. b) The ionization equilibrium in water is product-favored. c) The acid has at least one weak polar bond to a hydrogen atom. d) The ionization equilibrium in water is characterized by a large Ka. e) The acid dissociates completely in aqueous solutions. 20. A potential Brønsted-Lowry acid is a compound that . a) contains a H atom with a partial positive charge b) becomes a proton acceptor in aqueous solutions c) becomes a proton donor in aqueous solutions d) contains a H atom in a nonpolar covalent bond e) both a) and c) 21. A solution containing less than the equilibrium amount of solute is called . a) supersaturated b) unsaturated c) dilute d) concentrated e) saturated 22. Estimate the [OH – ] in a 1.0 × 10–3 M aqueous solution of Sr(OH)2. a) 1.0 × 10–2 M b) 1.0 × 10–3 M c) 0.5 × 10–3 M d) 0.02 M e) 2.0 × 10–3 M 23. Which compound below is MOST soluble in octane? a) CBr4 b) H2S c) H2O d) HOOC-CH2-COOH e) CH3-OH 24. Consider the ionization of phosphoric acid, H3PO4, in water and the pKa values associated with each ionization step. Rank the pKa values for H3PO4 from LOWEST to HIGHEST. a) pKa1 < pKa2 ≈ pKa3 b) pKa3 ≈ pKa2 < pKa1 c) pKa1 < pKa2 < pKa3 d) pKa1 < pKa3 < pKa2 e) pKa3 < pKa2 < pKa1 25. In an acidic solution at 25 oC, . a) pH = pKa -7 3 ] > 1.0 × 10 M c) pKb = pKa - -14 3 OH ] < 1.0 × 10 - -7 OH ] > 1.0 × 10 M 26. Consider the reaction below in a closed flask. At 200 oC, the equilibrium constant (Kp) is 2.40 × 103. 2 NO (g) N2 (g) + O2 (g) If 36.1 atm of NO (g) is added to the closed flask at 200 oC, what is the approximate partial pressure of O2 at equilibrium? a) 36.0 atm b) 294 atm c) 18.0 atm d) 6.00 atm e) 1.50 × 10-2 atm chem102w18_exam3c Answer Section MULTIPLE CHOICE 1. ANS: C PTS: 0 2. ANS: A PTS: 1 3. ANS: E PTS: 1 4. ANS: C PTS: 1 5. ANS: E PTS: 1 6. ANS: D PTS: 1 7. ANS: B PTS: 1 8. ANS: D PTS: 1 9. ANS: D PTS: 1 10. ANS: C PTS: 1 11. ANS: E PTS: 1 12. ANS: E PTS: 1 13. ANS: B PTS: 1 14. ANS: A PTS: 1 15. ANS: D PTS: 1 16. ANS: C PTS: 1 17. ANS: B PTS: 1 18. ANS: D PTS: 1 19. ANS: A PTS: 1 20. ANS: E PTS: 1 21. ANS: B PTS: 1 22. ANS: E PTS: 1 23. ANS: A PTS: 1 24. ANS: C PTS: 1 25. ANS: B PTS: 1 26. ANS: C PTS: 1