Practice Multiple Choice Questions on Electrochemistry

Practice Multiple Choice Questions on Electrochemistry

1. A piece of copper metal is placed into solutions containing each of the following three cations. Which ion will be reduced by the copper metal?

I. Sn​

II. Zn​

III. Ag​

(A) I only (B) II only (C) III only (D) I and II (E) I, II, and III

2. If 0.500 A of current is applied for 1.50 h to an electrolytic cell containing molten lithium chloride, how many grams of lithium would be deposited on the cathode?

(A)0.388 g (B)0.194 g (C) 0.097 g (D) 0.050 g (E) 5.4 x 10​

g

3. The reduction of 3.00 moles of Ca​

to Ca would require how many coulombs?

(A) 6.22 × 10​

C (B) 3.22 × 10​

C (C) 1.61 × 10​

C (D) 2.90 × 10​

C (E) 5.79 × 10​

C

4. A voltaic cell is created with one half-cell consisting of a copper electrode immersed in 1.0 M CuSO​

solution and the other half cell consisting of a lead electrode immersed in a 1.0 M Pb(NO​

)​

solution. Each half-cell is

main​tained at 25 °C. What is the cell potential, in volts?

(A) 0.47 V

(B) 0.21 V

(C) -0.21 V

(D) -0.47 V

(E) 2.50 V

Ag​

(aq) + Fe​

(aq) → Ag(s) + Fe​

(aq) 5. For the reaction above, what is the equilibrium constant at 25 °C?

(A) 1.0 (B) 1.6 (C) 3.2 (D) 6.4 (E) 10.0

6. If a current of 15.0A is applied to a solution of Cr​

ions, how long will it take to plate out 1.86 g of chromium metal?

(A) 3.83 minutes (B) 5.7 minutes (C) 11.5 minutes (D) 35.0 minutes (E) 690 minutes

7. A voltaic cell contains one half-cell with a zinc electrode in a Zn​

(aq) solution and a copper electrode in a Cu​

(aq) solution. At standard condition, E​

= 1.10 V. Which condition below would cause the cell potential to be greater than 1.10 V?

(A) 1.0 M Zn​

(aq), 1.0 M Cu​

(aq) (B) 5.0 M Zn​

(aq), 5.0 M Cu​

(aq) (C) 5.0 M Zn​

(aq), 1.0 M Cu​

(aq) (D) 0.5 M Zn​

(aq), 0.5 M Cu​

(aq) (E) 0.1 M Zn​

(aq), 1.0 M Cu​

(aq)

8. What is the standard free energy change (ΔG​

) for the reaction shown below?

Fe​

(aq) + Ag(s) → Fe​

(aq) + Ag​

(aq)

(A)-2.5 kJ

(B) 2.9 kJ

(C) 8.7 kJ

(D) 10.0 kJ

(E) 29 kJ

9. An electrolytic cell contains molten CuBr​

. What is the minimum voltage that must be applied to begin electrolysis?

(A) 0.17 V (B) 0.34 V (C) 0.73 V (D) 1.07 V (E) 1.41 V

Questions 10-13: The set of lettered choices is a list of ions that participate in oxidation reduction reactions. Select the one lettered choice that best fits each statement. A choice may be used once, more than once or not at all.

(A) C​

O​

(B) Cr​

O​

(C) MnO​

​

(D) NH​

(E) Sn​

10. Includes the species with the highest oxidation number.

11. Includes the species with the most negative oxidation number.

12. Reacts with reducing agent in acid solution such that the oxidation number of the metal becomes +3.

13. When oxidized, forms cation with charge of 4+

Questions 14-15:

Zn(s) + Cu​

(aq) → Zn​

(aq) + Cu(s) E​

= 1.10 volts

The above equation refers to the Daniell cell, a common electrochemical cell.

14. Which expression gives the value for ΔG​

in kJ/mol for this reaction?

(A) -2 × 8.31 × 1.10 ×1,000 (B) -2 ×96,500 × 1.10

8.31 (C) -2 × 96,500 × 1.10

1,000 (D) -2 × 96,500

1.10 ×8.31 (E) -2 × 8.31 × 1.10

1,000

15 . When the equilibrium constant for this reaction is reported in scientific notation, the exponent for 10 is closest to

(A) 0 (B) 5 (C) 10 (D) 20 (E) 40

Balance the following equation using the electron transfer method. You may wish to assign oxidation numbers and write the electronic equations for oxidation and reduction to help balance the overall reaction.

. ? . HNO​

+ . ? . P + . ? . H​

O → .? H​

PO​

+ . ? . NO

16. What is the sum of the coefficients in this balanced equation?

(A) 5

(B) 8

(C) 10

(D) 12

(E) 18

Questions 17-20: The diagram below represents apparatus that can be used in the laboratory for the electrolysis of a 1.0 M solution of KI. The terminals of the 12 volt DC power supply have been labeled with the appropriate charges.

The current is supplied at the rate of 2.5 amperes.

17. Which describes the behavior of I​

​(aq)​ ions in this system?

(A) I​

​(aq)​ ions migrate, as spectator ions, toward the anode.

(B) I​

​(aq)​ ions migrate toward the anode where they become oxidized to I​

​(aq) (C) I​

​(aq)​ ions migrate toward the anode where they become reduced to I​

​(aq) (D) I​

(aq) ​ions migrate toward the cathode where they become oxidized to I​

​(aq) (E) I​

​(aq) ​ions migrate toward the cathode where they become reduced to I​

(aq)

18. Which describes the behavior of K​

​(aq)​ ions in this system?

(A) K​

​(aq)​ ions migrate, as spectator ions, toward the cathode.

(B) K​

(aq) ​ions migrate toward the anode where they become oxidized to K(​s) (C) K​

(aq)​ ions migrate toward the anode where they become reduced to K​(s) (D) K​

(aq) ​ions migrate toward the cathode where they become oxidized to K​(s) (E) K​

(aq)​ ions migrate toward the cathode where they become reduced to K​(s)

19. Which best describes the behavior in the chamber containing the electrode at which bubbles of gas are observed?

(A) O​

(g)​ is produced as the pH of the solution increases.

(B) O​

(g) ​is produced as the pH of the solution decreases.

(C) H​

(g) ​is produced as the pH of the solution increases.

(D) H​

(g) ​is produced as the pH of the solution decreases.

(E) O​

(g) ​is produced as the pH of the solution remains the same.

20. Which expression gives the time in hours needed to produce 0.10 mol I​

(aq)?

(A) 0.10 × 2 2.5 ×60 (B) 0.10 × 96,500

2.5 × 60 x 60 (C) ​0.10 × 2

2.5 ×60 × 96,500 (D) 0.10 × 2 × 96,500

2.5 × 60 × 60

(E) 0.10 × 2 × 96,500 × 60 2.5

21. In the reaction: 2KMnO​

+ 3H​

SO​

+ 5H​

S → 5S + 2MnSO​

+ K2SO​

+ 8H​

O the oxidation number of sulfur changes from

(A) 0 to -2 (B) +5 to -5 (C) -2 to 0 (D) -5 to +5 (E) +6 to +4

Questions 22-24: The diagram below represents a standard Fe​

/Fe​

half cell con​nected to a standard Pb​

/Pb​

half cell. The electrodes are numbered for purposes of identification.

Pb​

(aq) + 2e- → Pb​

(s) E​

= -0.13 volts

Fe​

(aq) + e-→ Fe​

(aq) E​

= +0.77 volts

22. Which describes materials used for the construction of the standard Fe​

/Fe​

half cell?

I. The electrode is made of iron metal.

II. The source of Fe​

ions could be Fe(OH)​

III. The source of Fe​

ions could be Fe(NO​

)​

(A) I only (B) III only (C) II and III only (D) I and III only (E) I, II, and III

23. Which gives the changes in masses of the electrodes that occur during operation of the cell?

mass of electrode #1 mass of electrode #2

(A) decreases increases

(B) decreases remains the same

(C) remains the same decreases

(D) increases remains the same

(E) remains the same increases

24. Which expression gives the value of the standard potential for the cell in volts?

(A) 0.77 - 0.13 (B) 0.77 + 0.13 (C) 0.77 + (2 × 0.13) (D) 0.77 - (2 × 0.13) (E) 0.77 + (2 × (-0.13))

25. The order of chemical activity of three metals is X > Y > Z. Which describes the behavior of these metals?

I. Atoms of X can reduce atoms of Z.

II. Atoms of X can reduce cations of Z.

III. Atoms of Y can reduce cations of X.

(A) I only

(B) II only

(C) I and II only

(D) II and III only

(E) I, II, and III

26. When the value of E​

for a standard galvanic cell is greater than zero, which ranges apply to ΔG​

and K​

for the cell reaction?

Δ G​

​

K​

(A) <0 <0 (B) <0 >1 (C) >0 > 1 (D) <0 > 0 but < 1 (E) >0 > 0 but < 1

27. Which describes the oxidation number of nitrogen in NH​

NO​

?

(A) Both nitrogen atoms have the same oxidation number with the same sign (B) Both nitrogen atoms have the same oxidation number with opposite sign (C) The oxidation numbers of the two nitrogen atoms are +4 and +6, respectively.

(D) The oxidation numbers of the two nitrogen atoms are -3 and +5, respectively.

(E) The oxidation numbers of the two nitrogen atoms are -4 and +6, respectively.

28. A balanced half-reaction must illustrate conservation of

I. charge II. atoms III. molecules (A) I only

(B) I and II only (C) II only (D) II and III only (E) I, II, and III

29. Balance the following half-reaction in acid solution:

NO​

→ NH​

When balanced with the smallest whole-number coefficients possible, the sum of all the coefficients is

(A) 13

(B) 26

(C) 15

(D) 23

(E) 21

30. The standard reduction potential for PbO​

→ Pb​

is + 1.46 V, and the standard reduction potential for Fe​

→ Fe​

is +0.77 V. What is the standard cell voltage for the reaction?

4H​

+ PbO​

+2Fe​

→ 2Fe​

+Pb​

+2H​

O?

(A) -0.08 V (B) +0.69 V (C) +2.33 V (D) -0.69 V (E) -2.33 V

31. Which of the following compounds includes an element with an oxida​tion number of +5?

(A) ClO​

(B) MnO​

(C) NO​

(D) SO​

(E) NO​

32. Which of the following metals does NOT react with water to produce hydrogen?

(A) Zn (B) Li (C) Ca (D) Na (E) Rb

33. In the electrolysis of an aqueous solution of CuNO​

which of the following is expected to occur?

(A) Formation of O​

at the anode (B) Formation of H​

at the cathode

(C) Deposition of copper metal on the anode

(D) Formation of hydroxide ions at the cathode

(E) Formation of H​

at the cathode

34. Sodium metal cannot be electrolyzed from an aqueous Na​

SO​

solution because

(A) the voltage needed is too high for any available instrument to achieve (B) water is reduced to O​

before Na​

(C) Na ​

has a high over-potential that keeps it from being reduced (D) H​

has a more favorable reduction potential than Na​

(E) Na​

does electrolyze, but it immediately reacts with water again

35. Which of the following elements has the largest number of possible oxidation states?

(A) Fe (B) Cl (C) Ca (D) Mn (E) Na

36. Which of the following E​

values represents a nonspontaneous reac​tion that produces the greatest amount of product, assuming the same number of electrons is transferred in each reaction?

(A) +2.31 V (B) +0.23 V (C) -0.12 V (D) -1.68 V (E) -1.14 V

37. A metal is electrolyzed from aqueous solution by using an electrical current of 1.23 A for 2.5 h, and 3.37 g of metal is deposited. In a separate experiment the number of electrons used for the reduction of the metal is 2. What is the metal? ​

(A) Al

(B) Ni

(C) Sn

(D) Mg

(E) Au

38. Which of the following compounds includes an element that has the same oxidation number as the chlorine in sodium chlorate, NaClO​

?

(A) K​

Fe(CN)​

(B) KMnO​

(C) Al(NO​

)​

(D) (NH​

)​

SO​

(E) KClO​

39. With a current of 1.25 A, how many minutes will be required to deposit 2.00 g of copper on a platinum electrode from a copper (II) nitrate solution? (Faraday's constant = 96,485 C mol​

)

(A) 4859 (B) 81.0 (C) 40.5 (D) 1.35 (E) 2430

40. What is the minimum number of electrons needed to balance the following half-reaction with whole number coefficients?

IO​

→ I​

(A) 1 (B) 2 (C) 5 (D) 10 (E) 12

41. Which of the following pairs of constants are NOT mathematically related to each other?

(A) equilibrium constant and Gibbs free energy (B) rate constant and activation energy

(C) standard cell voltage and equilibrium constant

(D) standard cell voltage and rate constant

(E) Gibbs free energy and standard cell voltage.

42. Which of the following statements is FALSE?

(A) Reduction involves a gain of electrons.

(B) Batteries are galvanic cells.

(C) A spontaneous reaction always has a positive E​

(D) Electrolysis reactions always produce a gas at at least one elec​trode.

(E) Galvanic cells can be used to determine equilibrium constants.

43. The oxidation number of the nitrogen in the nitrate ion, NO​

is:

A. +1 B. +2 C. +3 D. +4 E. +5

44. Which will reduce Ag​

to Ag but not Ni​

to Ni?

Half-Reaction Reduction

Potential, E​

, volts

Mg​

(aq) + 2 e​

→ Mg (s) -2.363 Al​

(aq) + 3 e​

→ Al (s) -1.662 Zn​

(aq) + 2 e​

→ Zn (s) -0.763 Cd​

(aq) + 2 e​

→Cd (s) -0.410 Ni​

(aq) + 2 e​

→Ni (s) -0.230 Pb​

(aq) + 2 e​

→ Pb (s) -0.126 Ag​

(aq) + e​

→ Ag (s) +0.799

A. Al

B. Cd

C. Mg

D. Pb

E. Zn

45. For the reaction between permanganate ion and oxalate ion in basic solution, the unbalanced equation is:

2 MnO​

+ 3 C​

O​

→ 2 MnO​

+ CO​

Which is true regarding the number of OH​- ions when the equation is balanced with smallest, whole-number coefficients?

A. 0

B. 2 on the right

C. 2 on the left

D. 4 on the right

E. 4 on the left