Exam 2 Practice (Chapter 15-17)

Transcription

1 Exam 2 Practice (Chapter 15-17)

2 28. The equilibrium constant Kp for reaction (1) has a value of What is the value of the equilibrium constant for reaction (2)? (1) SO2 (g) + 1/2 O2(g) SO3 (g) Kp = (2) 2 SO3 (g) 2 SO2 (g) + O2 (g) Kp =? a) b) 2.24 c) 44.2 d) Kc = 278 for the reaction 2 SO2 (g) + O2 (g) 2 SO3 (g) at 1000 K. What is the value of Kp? a) b) c) 54.7 d) The reaction NH4HS (s) NH3 (g) + H2S (g) has Kc = 1.2 X 10 4 at 22 C. If a solid sample of NH4HS is placed in a closed container and allowed to decompose until equilibrium is reached, what will the equilibrium concentrations of NH3 and H2S be? a) M b) 0.28 M c) M d) 0.14 M 31. Consider the following reaction at equilibrium: N2 (g) + 3 H2 (g) 2 NH3 (g) H = kj The forward ( ) reaction should be favored by using conditions of a) high temperature and high pressure b) high temperature and low pressure c) low temperature and low pressure d) low temperature and high pressure

3 32. Write the equilibrium constant expression for the reactions below: a) CO2 (g) + H2 (g) CO (g) + H2O (l) b) SnO2 (s) + 2 CO (g) Sn (s) + 2 CO2 (g) c) 3 Fe (s) + 4 H2O (g) Fe3O4 (s) + 4 H2 (g) d) 6 CO2 (g) + 6 H2O (l) C6H12O6 (s) + 6 O2 (g)

4 33. Consider the following chemical reaction: H2 (g) + I2 (g) 2 HI (g) Kc = 49.5 at 440 C a) If the equilibrium concentrations of H2 and I2 are 0.25 M each, what is the equilibrium concentration of HI? b) If we start with H2 and I2 at 0.25 M each, what will the HI concentration be at equilibrium? c) If we start with H2 at 0.65 M, I2 at 0.65 M, and HI at 5.00 M, what is the value of Qc? Which way with the reaction go (forward, reverse, or no change) in order to react equilibrium?

5 Answers 28. D 29. D 30. C 31. D 32. a) Keq = [CO (g)] / [CO 2 (g)][h 2 (g)] b) Keq = [CO 2 (g)] 2 / [CO (g)] 2 c) Keq = [H 2 (g)] 4 / [H 2 O (g)] 4 d) Keq = [O 2 (g)] 6 / [CO 2 (g)] a) [HI]eq = 1.76 M b) [HI]eq = M c) Qc = > 49.5 The reverse ---reaction will occur until equilibrium is reached. Qc > Kc

6 Name CHEM 1412 Practice Exam 2, Chapters Zumdahl Kw = 1.0 X ph = pka + log ([conj. base]/[weak acid]) 1. In acidic solution a) [H + ] = [OH ] b) [H + ] < [OH ] c) [H + ] > [OH ] d) [H + ] = 1 M 2. What is the ph of a 0.15 M solution of HBr? a) 0.60 b) 0.82 c) 1.20 d) What is the concentration of H + ion in a solution of M sodium hydroxide? a) 1.6 X M b) 5.8 X 10 9 M c) 2.4 X M d) 1.9 X M 4. What is the hydroxide ion concentration of a 2.0 M solution of HCl? a) 3.8 X M b) 4.0 X M c) 4.6 X M d) 5.0 X M 5. Calculate the poh of a M NaOH solution. a) b) c) 2.00 d) What is the H + ion concentration in an NaOH solution if the ph is 13.24? a) 5.75 X M b) 2.29 X M c) 3.85 X M d) 1.36 X M 7. What is the ph of a M solution of Ca(OH)2? a) b) c) d) 12.33

7 8. A Bronsted-Lowry acid is defined as a substance that a) acts as a proton donor b) decreases [H + ] when dissolved in water c) increases [OH ] when dissolved in water d) acts as a proton acceptor 9. An Arrhenius base is defined as a substance that a) acts as an electron pair donor b) increases [H + ] when dissolved in water c) increases [OH ] when dissolved in water d) acts as a proton donor 10. A Lewis acid is defined as a substance that a) acts as an electron pair donor b) acts as an electron pair acceptor c) increases [H + ] when dissolved in water d) acts as a proton donor 11. What is the conjugate base of the bicarbonate ion, HCO3? a) H2CO3 b) CO3 2 c) HCO2 d) HCO4 12. What is the conjugate acid of the hydrogenphosphate ion, HPO4 2? a) H3PO4 b) PO4 3 c) H2PO4 d) H2PO Which of the following is a strong acid? a) HNO2 b) HClO c) H2SO4 d) H2SO3 14. Which of the following is a weak acid? a) HC2H3O2 b) HCl c) HBr d) HNO3 15. Which of the following is a strong base? a) NaF b) NaCl c) CsOH d) KC2H3O2 16. Which of the following is a weak base? a) LiNO2 b) NaNO3 c) NH4Cl d) LiBr 17. Which is a conjugate pair? a) HF and NaF b) NaF and KF c) HF and HCl d) HNO2 and HNO3 18. Which is the strongest acid? a) HClO3 b) HBrO3 c) HBrO4 d) HClO4 19. Which one of the following solutions would be acidic (have a ph < 7)? a) NaBr (aq) b) NaF (aq) c) NaNO2 (aq) d) NH4Cl (aq)

8 20. Based on its Ka value, which of the following is the weakest acid? a) HF, Ka = 6.8 X 10 4 b) HClO, Ka = 3.0 X 10 8 c) HNO2, Ka = 4.5 X 10 4 d) HCN, Ka = 4.9 X Which of the following pairs could be used to make a buffer solution? a) KC2H3O2 and NaC2H3O2 b) NH4Br and NH4Cl c) HC2H3O2 and NaC2H3O2 d) NaOH and HCl 22. Complete the equation for the first dissociation of the weak acid H2CO3 in aqueous solution: H2CO3 (aq) a) 2 H + (aq) + CO3 2 (aq) b) H + (aq) + HCO3 (aq) c) HCO3 (aq) + OH (aq) d) H + (aq) + OH (aq) 23. Complete the net ionic reaction of the hydrolysis of the weak base Na2SO3: SO3 2 (aq) + H2O (l) a) H2SO3 (aq) + 2 OH (aq) b) HSO3 (aq) + H + (aq) c) 2 Na + (aq) + 2 OH (aq) d) HSO3 (aq) + OH (aq) 24. The equation for the solution of the slightly soluble solid PbI2 in water is, a) PbI2 (aq) Pb 2+ (aq) + I2 2 (aq) b) PbI2 (s) Pb (aq) + I2 (aq) c) PbI2 (s) Pb 2+ (aq) + 2 I (aq) d) Pb 2+ (aq) + 2 I (aq) PbI2 (s) 25. Calculate the ph of a solution of 0.25 M hypobromous acid, HBrO. Ka for HBrO is 2.1 X a) 8.62 b) 5.73 c) 4.64 d) Calculate the ph of a 0.25 M solution of sodium hypobromite, NaBrO. The Ka of hypobromous acid, HBrO, is 2.1 X a) 9.15 b) c) 6.41 d) 4.88

9 27. An unknown weak acid HA was titrated with NaOH while monitoring the ph of the solution with a ph meter. The equivalence point was reached after ml of the NaOH solution was added. The ph after half of this volume of NaOH was added was What is the value of Ka of the acid? a) 6.5 X 10 5 b) 4.4 X 10 6 c) 2.3 X 10 8 d) 1.78 X What is the molarity of an H2SO4 solution if 25.0 ml of this solution required 27.2 ml of M NaOH to completely neutralize the acid in a titration (forming Na2SO4)? a) M b) M c) M d) M 29. What is the ph of a solution that is 0.10 M in HClO and 0.25 M in NaClO? Ka for HClO is 3.0 X a) 5.22 b) 7.38 c) 7.92 d) Calculate the molar solubility of ferric hydroxide, Fe(OH)3. Ksp for Fe(OH)3 = 1.6 X a) 9.5 X M b) 6.7 X 10 9 M c) 4.3 X 10 6 M d) 8.8 X M

10 Answer Key 1. C 2. B 3. A 4. D 5. D 6. A 7. C 8. A 9. C 10. B 11. B 12. C 13. C 14. A 15. C 16. A 17. A 18. D 19. D 20. D 21. C 22. B 23. D 24. C 25. C 26. B 27. A 28. B 29. C 30. D