15 Electrochemistry Practice Problems for DAT Exam Prep

X. Electrochemistry

Electrochemistry practice problems

There are a total of 15 electrochemistry practice problems, which are important content-oriented in the summary part of this chapter. Approximately 1 minute is given per question in each test. After the test, if you press the “See Result” button, the results will be displayed along with the answer choices. Red marks indicate incorrect answers and green marks indicate correct answers. Explanations or solutions to the questions are displayed below each question.

ELECTROCHEMISTRY TEST 1

1 / 15

Which of the following is a strong candidate for the reaction at anode in a galvanic cell?

(Reactions are reversible.)

X + Y²⁺ → X²⁺ + Y

A. Cd(s) → Cd²⁺(aq) + 2e^– E° = +0.40V

B. I₂(s) + 2e⁻ → 2I⁻(aq) E° = +0.54 V

C. 2Cl^–(aq) → Cl₂(g) + 2e^– E° = -1.36V

D. Mg(s) → Mg²⁺(aq) + 2e^– E° = +2.37V

E. 2H⁺(aq) + 2e^– → H₂(g) E° = 0.00V

2 / 15

A. The strongest reducing agent is Na⁺.

B. The strongest oxidation agent is Cl₂.

C. The reaction of the strongest reduction is IV.

D. The strongest reaction at anode is I.

E. The spontaneous reaction from the II and III can produce + 1.1V of cell potential.

3 / 15

A. 2Na(s) + Zn²⁺(aq) → 2Na⁺(aq) + Zn(s)

B. Zn(s) + 2H⁺(aq) → Zn²⁺(aq) + H₂(g)

C. 2Na(s) + Cu²⁺(aq) → 2Na⁺(aq) + Cu(s)

D. 2H⁺(aq) + Cu(s) → H₂(g) + Cu²⁺(aq)

E. Zn(s) + Cu²⁺(aq) → Zn²⁺(aq) + Cu(s)

4 / 15

Which of the following is an INCORRECT statement for the reaction?

Zn(s)|Zn²⁺(aq)||Cu²⁺(aq)|Cu(s)

Total E^o = +1.1V

A. There is a salt bridge.

B. The reaction at anode is Zn(s) → Zn²⁺(aq) + 2e^–.

C. The reduction reaction is Cu²⁺(aq) + 2e^– → Cu(s).

D. Electro flow is from Cu(s) to Zn(s).

E. This is a galvanic cell.

5 / 15

From the shorthand notation,

Ag(s)|Ag⁺(aq)||Cl₂(g)|Cl^–(aq),

the total E^o is 0.56V. Find the value of x from the reduction half-reaction for Ag(s) below.

Ag⁺(aq) + e^– → Ag(s) E^o= x V

Cl₂(g) + 2e^– → 2Cl^– (aq) E^o= 1.36 V

A. +0.4

B. -0.4

C. +0.8

D. -0.8

E. +1.6

6 / 15

The following formula represents two reduction half-reactions.

Ag⁺(aq) + e^– → Ag(s) E^o = +0.8V

Cd²⁺(aq) + 2e^– → Cd(s) E^o = -0.4V

How much cell potential would be produced for a galvanic cell?

A. +0.4 V

B. +1.2 V

C. -1.2 V

D. +2.0 V

E. -2.0 V

7 / 15

Which of the following is an INCORRECT statement about electrochemical cells?

A. Voltaic and Daniell cells are ΔG < 0.

B. Daniell cells have a salt bridge to keep electrical neutral solution.

C. An external power source drives the nonspontaneous reaction in an electrolytic cell.

D. Hydrogen-bubble polarization can reduce current in a simple voltaic cell.

E. None of these answers are incorrect. All are correct.

8 / 15

As compared to electrolytic cells, which of the following are the correct pairs for galvanic cells?

A. ΔG: + Total E°: – Anode: + Cathode: –

B. ΔG: + Total E°: + Anode: – Cathode: +

C. ΔG: – Total E°: + Anode: – Cathode: +

D. ΔG: – Total E°: + Anode: + Cathode: –

E. ΔG: + Total E°: – Anode: – Cathode: +

9 / 15

For an electrolytic cell driving a nonspontaneous reaction under standard conditions, which combination of reaction ΔG°, cell E°, and electrode signs is correct?

A. ΔG: + Total E°: – Anode: + Cathode: –

B. ΔG°: −; E°cell: +; Anode: −; Cathode: +

C. ΔG°: +; E°cell: −; Anode: −; Cathode: +

D. ΔG°: −; E°cell: +; Anode: +; Cathode: −

E. ΔG°: +; E°cell: +; Anode: +; Cathode: −

10 / 15

The standard free-energy change, ΔG, is – 579kJ when the value of E^o is 2V. How many electrons are transferred?

A. 2

B. 3

C. 4

D. 5

E. 6

11 / 15

When an aqueous solution of CuCl₂ is electrolyzed in a cell, what is the standard free-energy change, DG, from the reaction?

Cl₂(g) + 2e^– → 2Cl^–(aq) E^o = 1.36V

Cu²⁺(aq) + 2e^– → Cu(s) E^o = 0.34V

A.+98kJ

B. -98kJ

C. +197kJ

D. -197kJ

E. +393kJ

12 / 15

A constant current of 2.5A is passed through the solution of AgNO₃ for 2 minutes. What charge, in coulombs, passes through the solution?

A. 1.25

B. 5

C. 50

D. 150

E. 300

13 / 15

A constant current passes through an electrolysis cell for 2 hours 40 minutes 50 seconds. If the total charge passed is 0.010 faraday (use 1 faraday = 96500 C), what is the current in amperes?

A. 0.01A

B. 0.02A

C. 0.1A

D. 0.2A

E. 1.0 A

14 / 15

When a charge of 3 faradays passes through molten MgCl₂, how many moles of Mg are deposited? Assume 100% current efficiency.

Mg²⁺ + 2e⁻ → Mg(s)

A. 0.7

B. 1.5

C. 2.0

D. 3.0

E. 6.0

15 / 15

What volume of H₂ are produced when the aqueous solution of NaBr is electrolyzed in a container for 1 hour 20 minutes 25 seconds with a constant current of 2A at STP (273 K, 1 atm), assuming 100% current efficiency?

2H₂O(l) + 2Br^–(aq) → Br₂(l) + H₂(g) + 2OH^–(aq)

A. 1.12 L

B. 4.4L

C. 8.8L

D. 17.6L

E. 35.2L

Your score is

The average score is 17%

Reduction half-reaction
Oxidation and reduction

Shorthand notation
Oxidation and reduction
Multiply coefficient to cancel electrons