CHM 2046 EXAM 3 FORM CODE A 04/07/2011
Please bubble in your name, UFID #, and form code on the answer sheet using a #2 pencil.
The form code for this exam is form code A.
1. Which statement is false?
(a) In a voltaic cell, the anode is negative relative to the cathode.
(b) Oxidation occurs at the anode of a voltaic or an electrolytic cell.
(c) Electrons flow into the cathode of an electrolytic cell.
(d) A metal that plates out of an electrolytic cell appears on the cathode.
(e) The cell electrolyte provides a solution of mobile electrons.
2. What is the function of a salt bridge in a voltaic cell?
(a) To transport anions from the anodic half cell to the cathodic half cell
(b) To transport electrons from the anodic half cell to the cathodic half cell
(c) To transport cations from the cathodic half cell to the anodic half cell
(d) To transport electrons from the cathodic half cell to the anodic half cell
(e) To transport anions from the cathodic half cell to the anodic half cell
3. Which statement is true about homogenous electron-transfer reactions?
(a) They occur at an interface.
(b) They take place at both the anode and cathode in voltaic cells.
(c) They take place at both the anode and cathode in electrolytic cells.
(d) They always take place in the same phase.
(e) They always take place in two different phases.
4. A galvanic electrochemical cell is:
(a) A cell where electrons flow from cathode to anode.
(b) A cell that requires a battery to make it run.
(c) A cell that has a negative free energy change for the cell reaction.
(d) A cell used in the production of galvanized metals.
(e) A cell that converts electrical energy into chemical energy.
5. The anode in an electrochemical cell is:
(a) The electrode where oxidation occurs
(b) The electrode where reduction occurs
(c) The electrode that repels anions
(d) Both (a) and (c) are correct.
(e) Both (b) and (c) are correct.
6. Calculate ΔS rxn for the following reaction at 298 K: C H 3g)8+ 5 O (g) 2 3 CO 2g) + 4H O 2g)
given the following standard entropy values: C H (g3 289.9 J/K mol, O (g) 205.29 J/K mol, CO (g) 213.7 J/2
mol, H O2(g) 188.72 J/K mol.
(a) 57.58 J/K (b) 105.6 J/K (c) 96.58 J/K (d) 56.3 J/K (e) 100.63 J/K
7. At 298 K ΔS rxn0for the following reaction is -172.6 kJ/K: 2 CO (g) + O (g) 2 2 CO (2). Calculate ΔS univ, and
state whether the reaction is spontaneous at this temperature given H of CO(g) = –110.5 kJ/mol, CO (g) = –
(a) 170.7 J/K, spontaneous (b) -170.7 J/K, nonspontaneous (c) -169.2 J/K, nonspontaneous
(d) -169.2 J/K, spontaneous (e)-170.7 J/K, spontaneous
8. Calculate ΔG° at 298 K for the following reaction with ΔS° surr 4794 J/K:
C 2 (6) + 7/2 O (g2 → 2CO (g) + 2H O (g) gi2en the following S° values (J/mol∙K) at 298 K: C H (g) = 2 6
229.2, O (g) = 205.1, CO (g) = 213.7, H O (g) = 188.8.
2 2 2
(a) 4.841 kJ (b) - 14.0 kJ (c) 14.0 kJ (d) - 1443 kJ (e) 1443 kJ
9. The second law of thermodynamics states that:
(a) Energy is conserved.
(b) A spontaneous process occurs in the direction that increases the entropy of universe.
(c) A spontaneous process occurs in the direction that decreases the entropy of universe.
(d) Energy cannot be created or destroyed.
(e) A perfect crystal has zero entropy.
10. The third law of thermodynamics states that:
(a) A perfect crystal has zero entropy at standard state.
(b) A perfect crystal has infinite entropy at room temperature.
(c) A perfect crystal has zero entropy at room temperature.
(d) Both (a) and (c)
(e) A perfect crystal has zero entropy at zero Kelvin. 11. Calculate the G° for a reaction at 25 °C given that K = 1.8x10eq 11
(a) -64.2 kJ (b) 64.2kJ (c) 118 kJ (d) - 642 J (e) 14 kJ
12. The Haber process for the production of ammonia involves the reaction
N 2g) + 3 H 2(g) → 2NH (g)3