PORTAGE LEARNING CHEM 104 FINAL EXAM QUESTIONS AND ANSWERS

PORTAGE LEARNING CHEM 104 FINAL EXAM QUESTIONS AND ANSWERS Which of the following combinations represent a weak acid and weak base conjugate pair? a. HCl and NaCl b. KH2PO4 and Na3PO4 c. CH3COOH and KCH3COO d. both choice b and choice c e. choice a, choice b and choice c - ANSWER c. CH3COOH and KCH3COO What is the pH of 0.050M HClO4? a. 0.90 b. 1.3 c. 3.0 d. 7.0 e. 12.7 - ANSWER b. 1.3 What is the pH of 0.080M NH3? a. 1.1 b. 2.9 c. 8.8 d. 11.1 e. 12.9 - ANSWER d. 11.1 Which of the following three salts would be basic if dissolved in water? I. KNO2 II. NH4Cl III. Zn(NO3)2 a. I only b. II only c. III only d. I and II only e. all three - ANSWER a. I only What is the pH of 0.80M KHCO3? a. 3.2 b. 5.2 c. 8.3 d. 8.8 e. 10.8 - ANSWER c. 8.3 The base dissociation constant, Kb, for HAsO4 2- is: a. 2.00 x 10E-12 b. 6.00 x 10E-10 c. 8.00 x 10E-8 d. 1.25 x 10E-7 e. 1.67 x 10E-5 - ANSWER d. 1.25 x 10E-7 Which of the following would you choose to make a buffer with a pH at around 9.2? a. HCl and NaCl b. HOCl and KOCl c. HCN and NaCN d. H3PO4 and KH2PO4 e. NaHSO4 and Na2SO4 - ANSWER c. HCN and NaCN What is the buffer range for the Na2HPO4/Na3PO4 buffer if its pH = 11.9? a. 1.1 to 3.1 b. 6.2 to 8.2 c. 9.9 to 11.9 d. 10.9 to 12.9 e. 11.3 to 13.3 - ANSWER e. 11.3 to 13.3 What is the concentration of a Ca(OH)2 solution if its pH is 13.5? a. 0.16 b. 0.32 c. 0.64 d. 3.2 x 10-14 e. 6.4 x 10-14 - ANSWER a. 0.16 What is the concentration of an HF solution if its pH is 1.7? a. 0.57 b. 0.027 c. 0.020 d. 7.2 x 10-4 e. 5.0 x 10-13 - ANSWER a. 0.57 What is the pH of an aqueous solution that is made by mixing 200 mL of 0.20M NaH2PO4 and 200 mL of 0.60M Na2HPO4 at 25oC? a. 1.6 b. 2.6 c. 6.7 d. 7.2 e. 7.7 - ANSWER e. 7.7 What is the pH of an aqueous solution that is made by mixing 0.50 L of 0.40M KOH and 0.50L of 0.60M HBr at 25oC? a. 0.52 b. 0.70 c. 1.0 d. 13.3 e. 13.5 - ANSWER c. 1.0 Which one of the following statements is always true? a. For a gas phase reaction, if K value is very large the equilibrium position will be reached faster. b. For any gas phase reaction, the value of K always increases when temperature increases. c. For any gas phase reaction, the equilibrium position always changes with a change in pressure. d. The equilibrium position depends on the initial concentrations of the reactants and products. e. The value of equilibrium constant depends on the amounts of reactants and products mixed together initially. - ANSWER d. The equilibrium position depends on the initial concentrations of the reactants and products. Titration curve produced in titration of __________ will have an equivalence point with pH 7. a. HClO3(aq) with NaOH(aq) b. HClO2(aq) with NaOH(aq) c. NH3(aq) with HClO3(aq) d. LiOH(aq) with HClO3(aq) e. Both c and d - ANSWER b. HClO2(aq) with NaOH(aq) Given: 2NO2(brown gas) ⇌ N2O4(colorless gas), Kc = 3 at 400K You have a sealed rigid glass flask containing an equilibrium mixture of NO2(g) and N2O4(g) at room temperature. The mixture appears dark brown. When you submerge the flask with the gases in boiling water the color of the mixture becomes lighter. What is the possible explanation for this phenomenon? a. The pressure of gases in the rigid container will be greater at higher temperature and the equilibrium position will shift to the left. b. The pressure of gases in the rigid container will be greater at higher temperature and the equilibrium position will shift to the right. c. The reaction is exothermic, so when you increase the temperature the equilibrium position shifts to the left. d. The reaction is exothermic, so when you increase the temperature the equilibrium position shifts to the right. e. Both a and d are true. - ANSWER b. The pressure of gases in the rigid container will be greater at higher temperature and the equilibrium position will shift to the right. Mg(OH)2 has a very low solubility in pure water at room temperature. According to Le Chatelier's principle, this hydroxide will be more soluble in _________ solution than in pure water at the same temperature. a. NH4OH(aq) b. NH4Cl(aq) c. NaOH(aq) d. MgCl2(aq) e. HCl(aq) - ANSWER e. HCl(aq) Which of the following mixtures will not produce a buffered solution?