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2 Form a 1 NAME: General Chemistry 116 Exam 2 Summer 2007 Each question is worth 5 points. 1. BiI 3 has K sp of 8.1 x at 25 degrees C. Solid BiI 3 is added to water at 25 degrees C and stirred until equilibrium is reached. What is the concentration of BiI 3 in molarity? a x 10-8 M b x M c x M d x 10-6 M e x 10-7 M f x 10-5 M g x M h x 10-7 M 2. Solid Ag 2 CrO 4 is added to 1.00 L water at 25.0 degrees C and stirred until equilibrium is reached grams dissolved. What is the Ksp for Ag 2 CrO 4? a x M b x M c x M d x M e x 10-9 M f x M g x M h x M 3. Consider the reaction below M CO and 1.00 M H 2 O are in a one liter flask and the system is allowed to reach equilibrium. What is final concentration of CO? Kc at this temperature is CO(g) + H 2 O(g) = CO 2 (g) + H 2 (g) a M b M c M d M e x 10-2 M f M g x 10-1 M h M i M j M

3 Form a 2 4. Consider the following equilibrium at 25.0 degrees C and the information about initial concentrations, and answer two questions: CH 4 (g) + 2H 2 S(g) = CS 2 (g) + 4H 2 (g) In one experiment, 4.00 M CH 4, 4.00 M CS 2, 8.00 M H 2 S and 8.00 M H 2 in a 1.00 L vessel at 1000 degrees C. Kc is a. What is Q? a. 556 b c d e x 10-2 f g x 10-3 h i j b. After the system is allowed to reach equilibrium, which of the following concentrations for H 2 and H 2 S are reasonable, given the above initial concentrations? (Only one set of values is reasonable) a. H 2 S = 3.66 M; H 2 = 13.8 M b. H 2 S = M ; H 2 = 1.76 M c. H 2 S = M; H 2 = 10.4 M d. H 2 S = 6.35 M; H 2 = 8.50 M e. H 2 S = 7.28 M; 15.9 M 5. Consider the following reaction CO(g) + H 2 O(g) = CO 2 (g) + H 2 (g) Consider the above reaction M CO and 2.00 M H 2 O are in a one liter flask and the system is allowed to reach equilibrium. What is final concentration of CO? Kc at this temperature is a M b M c x 10-2 M d x 10-1 M e M f M g M h M i M j M

4 Form a ml of buffer solution is composed of M formic acid (HCO 2 H) and M sodium formate (NaHCO 2 ). What is the ph of the buffer solution after the addition of mole HCl? (assume no volume change) HCO 2 H = HCO H + K a = 1.8 x 10-4 a b c d e f g h i j ml of M HCl is titrated with M NaOH. What is the ph of the solution after the addition of 75.0 ml of NaOH? a b c d e f g h Answer two questions. a. Predict whether the equilibrium below will favor products or reactants, Refer to the table of acid and base strengths at the back of the exam. CN - (aq) + HNO 2 (aq) = HCN(aq) + NO 2 - (aq) a. products b. reactants b. Use the following information to determine which of the following is an acidic salt. HNO 3 is a strong acid. pkb of NH 3 is 1.8 x pka HF is 7.1 x 10-4 pka of HCN 4.9 x a. NH 4 F b. LiCN c. Li NO 3 d. NH 4 CN e. LiF

5 Form a 4 9. This question has two parts. a. Refer to this equation: 2CO 2 (g) -= 2CO (g) + O 2 (g) delta H = -514kJ The amount of CO produced by this reaction can be maximized by carry out the reaction at a. high temperature and high pressure b. high temperature and low pressure c. low temperature and low pressure d. low temperature and high pressure b. Refer to this equation 2NH 3 (g) = 2N 2 (g) + 3H 2 (g) delta H = 92.4 kj Suppose the system is at equilibrium. Adding N 2 (g) to this system will: a. decrease the concentration of NH 3 (g) at equilibrium b. decrease the concentration of H 2 (g) at equilibrium c. increase the concentration of H 2 (g) at equilibrium d. increase the value of the equilibrium constant 10. Calculate the percent ionization of a M solution of HN 3. HN 3 (aq) = H + (aq) + N 3 - (aq) Ka = 1.9 x 10-5 a % b % c % d % e % f % g % h % ml of a M solution of NH 3 is mixed with 200 ml of a M solution of HCl. What is the concentration of NH 3 in the resulting solution? NH 3 (aq) + H 2 O(l) = OH - (aq) + NH 4 + (aq) Kb = 1.8 x 10-5 a. 9.3 x 10-7 M b. 3.5 x M c. 3.6 x M d. 2.7 x 10-8 M e. 2.7 x 10-3 M f. 8.2 x 10-4 M g. 1.0 x 10-5 M h x 10-6 M

6 Form a CaF 2 is added to water and stirred. After equilibrium is established, it is determined` that the [F - ] is 4.8 x 10-4 M. What is K sp? a. 7.5 x b. 1.6 x c. 7.2 x d. 5.5 x e. 5.1 x f. 9.2 x g. 8.3 x h. 4.0 x ml of 2.50 x 10-3 molar Ba(CN) 2 and 650 ml of 3.00 x 10-4 molar Cd(NO 3 ) 2 are mixed. Answer two questions. Assume Ba(CN) 2, Cd(NO 3 ) 2 and Ba(NO 3 ) 2 are soluble. Ksp for Cd(CN) 2 is 1.0 x 10-8 a. Will Cd(CN) 2 precipitate? a. yes b. no b. What is Q? a x b x c x d x e x f x g x 10-6 h x ml of a M hypochlorous acid is titrated with M KOH. Calculate the ph at the equivalence point when 45.0 mls of M KOH has been added. HOCl(aq) = H + (aq) + OCl - (aq) K a = 3.5 x 10-8 a b c d e f g h. 10.9

7 Form a ml of a M hypochlorous acid is titrated with M KOH. Calculate the ph when 0.0 mls M KOH has been added. HOCl(aq) = H + (aq) + OCl - (aq) K a = 3.5 x 10-8 a b c d e f g h ml of a M hypochlorous acid is titrated with M KOH. Calculate the ph when 27.0 mls M KOH has been added. HOCl(aq) = H + (aq) + OCl - (aq) K a = 3.5 x 10-8 a b c d e f g h Refer to the following equation. C 6 H 6 (g) + 3H 2 (g) = C 6 H 12 (g) When 1.00 M C 6 H 6 and 3.00 M H 2 are placed in a L container and allowed to reach equilibrium at elevated temperature, the resulting mixture contains M C 6 H 6. What is the value for K c at this temperature? a x 10-2 b x 10-2 c x 10-4 d x 10-1 e x 10 4 f g h i x 10-4 j Which statement is true? a. If a solution has a ph of 11.0, there are more H + ions in this solution then there are in pure water. b. If the poh of a solution is 2, the solution is acidic. c. A M solution of KOH will have a poh that is greater than 7. d. A poh 3.0 solution has a higher concentration of H + than a ph 3.0 solution. e. A ph 12.0 solution has a greater OH - concentration of than a poh 12 solution.

8 Form a What is the ph of a solution of Ba(OH) 2 a b c d e f g h The ph of a 0.35 M solution of sodium hypoiodate, NaOI is Calculate the Ka of HOI. HOI (aq) = H + (aq) + OI - (aq) Ka =? a x 10-5 b. 2.7 x c. 4.2 x 10-8 d. 5.8 x e. 3.8 x 10-6 f. 9.2 x 10-6 g. 4.9 x 10-9 h. 8.5 x What is the equilibrium concentration of HCO 2 - in a 0.50 M solution of H 2 CO 2? Refer to these equations: H 2 CO 2 = HCO H + K a1 = 4.2 x 10-7 HCO 2 - = CO H + K a2 = 4.8 x a. 6.9 x 10-8 M b M c. 3.9 x 10-3 M d. 7.2 x 10-3 M e. 8.1 x 10-6 M f. 4.6 x 10-4 M g. 4.1 x 10-7 M h. 3.6 x 10-9 M

9 Form a You wish to prepare a buffer solution of ph 4.30 using CH 3 COOH and Na + CH 3 COO -. CH 3 COOH(aq) = H + (aq) + CH 3 COO - (aq) K a = 1.8 x 10-5 If you use mole CH 3 COOH per liter, how many mole Na + CH 3 COO - per liter should you add Na + CH 3 COO -? a mol/liter b mol/liter c mol/liter d x 10-1 mol/liter e mol/liter f mol/liter g mol/liter h x 10-2 mol/liter 23. What is the HC 7 H 5 O 2 concentration in a 0.080M sodium benzoate (Na C 7 H 5 O 2 ) solution? The acid equilibrium for benzoic acid is as follows. HC 7 H 5 O 2 (aq) = H + (aq) + C 7 H 5 O 2 - (aq) Ka = 6.3 x 10-5 a. 5.6 x 10-2 M b. 8.1 x 10-6 M c. 3.2 x 10-2 M d. 3.6 x 10-6 M e. 1.8 x 10-4 M f. 1.2 x 10-4 M g. 6.9 x 10-3 M h. 2.9 x 10-8 M