1. Electrochemistry Review

2. Which is a very strong reducing agent?10
MnO4- H+ H2 Na
Na+ 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

3. By definition, the reduction potential for this species is equal to zero.10
MnO4- H+ H2 Na
Na+ 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

4. This is a very strong oxidizing agent.10
MnO4- H+ H2 Na
Na+ 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

5. How many electrons are transferred in the following reaction: MnO4- + Cr + 2H2O  MnO2 + Cr OH- 10 1 2 3 4 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

6. In which of the following molecules does hydrogen have an oxidation state of -1?10
H2O
NH3
CaH2
CH4 H2 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

7. Cu has been oxidized by H+ Cu has been oxidized by NO3-
When solid copper shavings are placed in a solution of dilute HNO3, Cu2+ ions appear and NO gas bubbles form. Which of the following has occurred? 10
Cu has been oxidized by H+
Cu has been oxidized by NO3-
Cu has been reduced by NO3-
NO3- has been oxidized by H+
NO3- has been reduced by H+ 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

8. 4820 coulombs 9650 coulombs 19300 coulombs 38600 coulombs
The half reaction at the anode of a galvanic cell is as follows: Zn (s)  Zn2+ + 2e- What is the maximum charge, in coulombs, that can be delivered by a cell with an anode composed of 6.54 g of zinc? 10
4820 coulombs
9650 coulombs
19300 coulombs
38600 coulombs
48200 coulombs 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

9. Q will increase and E will decrease
Ni(s) + Cu2+  Ni2+ + Cu(s) The reaction above takes place in a galvanic cell. If the initial concentration of Ni2+ is increased while the initial concentration of Cu2+ remains the same, what will be the effect on Q and E? 10
Q and E will increase
Q and E will decrease
Q will increase and E will decrease
Q will decrease and E will increase
Q and E will not change 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

10. Mn2+ + Cu  Mn + Cu2+ Mn2+ + Zn  Mn + Zn2+ Zn2+ + Cu  Zn + Cu2+
Look up the reduction potentials for Cu2+, Zn2+, and Mn2+ . Which of the following reactions will occur spontaneously? 10
Mn2+ + Cu  Mn + Cu2+
Mn2+ + Zn  Mn + Zn2+
Zn2+ + Cu  Zn + Cu2+
Zn2+ + Mn  Zn + Mn2+
Cu2+ + Zn2+  Cu + Zn 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

11. E = 2.40 V, and the reaction is not spontaneous
Which of the following statements is true for the following reaction taking place under standard conditions? Al(s) + Cr3+  Al3+ + Cr(s) 10
E = 2.40 V, and the reaction is not spontaneous
E = 0.92 V, and the reaction is spontaneous
E = V, and the reaction is not spontaneous
E = V, and the reaction is spontaneous
E = V, and the reaction is not spontaneous 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

12. What is the reaction potential for the following reaction
What is the reaction potential for the following reaction? Fe2+ + Cu  Fe + Cu2+ 10
-0.7 V
-0.1 V
0.1 V
0.7 V
1.4 V 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

13. What is the standard potential for the cell?
An electrochemical cell was created by placing a zinc electrode in a 1.00 M solution of ZnSO4 and placing a copper electrode in a 1.00 M solution of CuSO4. The two compartments are connected by a salt bridge, and the following reaction occurred at 25oC. Zn(s) + Cu2+  Zn2+ + Cu(s)
What is the standard potential for the cell?
How much work can the cell do?
What is the value of Keq for the reaction?
At a certain point in the progress of the reaction, [Cu2+] drops to 0.10 M and [Zn2+] increases to 1.90 M. What is the cell potential at this point?

14. What was the mass of solid silver produced in the electrolysis?
An 800 mL sample of M Ag+ solution was electrolyzed, resulting in the formation of solid silver and oxygen gas. The solution was subjected to a current of 2.00 A for 10.0 minutes. The solution became progressively more acidic as the reaction progressed.
Write the two half-reactions that occur, stating which takes place at the anode and which the cathode.
If the oxygen gas produced in the electrolysis was collected at STP, what was its volume?
What was the mass of solid silver produced in the electrolysis?
If the solution was neutral at the start of the electrolysis, what was the pH of the solution when the process was complete?

15. Identify the oxidizing agent for the spontaneous reaction.
Sr(s) + Mg2+ < -- > Sr2+ + Mg(s) Consider the reaction above that occurs at 25oC. All reactants and products are in their standard states. The value of Keq for the reaction is 4.2 x 1017 at 25o C.
Predict the sign of the standard cell potential for a cell based on the reaction. Explain your prediction.
Identify the oxidizing agent for the spontaneous reaction.
If the reaction were carried out at 60oC instead of 25oC, how would the cell potential change? Justify your answer.
How would the cell potential change if the reaction were carried out at 25oC with a 1.0 M solution of Mg(NO3)2 and a 0.10 M solution of Sr(NO3)2 ? Explain.
When the cell described above reaches equilibrium, what is the cell potential?