Question

A standard galvanic cell is constructed in which a Cd²⁺ | Cd half cell acts as the cathode. Which of the following statements are correct?

Hint: Refer to a table of standard reduction potentials.

(Choose all that apply.)

1. The anode compartment could be F₂|F^-.

2. The anode reaction could be Cr -> Cr³⁺ + 3e^-

3. Cd²⁺ is reduced at the cathode.

4. As the cell runs, anions will migrate from the Cd²⁺|Cd compartment to the other compartment.

5. The cathode reaction is Cd -> Cd²⁺ + 2e^-

Answer 1

Ans :- The correct statements are :-

(2). The anode reaction could be Cr -> Cr³⁺ + 3e^-

(3). Cd²⁺ is reduced at the cathode.

Explanation :-

(1).  The anode compartment could be F₂|F^- is Incorrect, because Standard reduction potential of Fluorine is + 2.87 V (i.e. E⁰_F2/F- = + 2.87 V) therefore Fluorine can never act as reducing agent for Cd whose Standard reduction potential is

- 0.40 V ( i.e. E⁰_Cd+2/Cd = - 0.40 V).

Note :- More negative value of standard reduction potential stronger will be the reducing agent.

(2). The anode reaction could be Cr -> Cr³⁺ + 3e^- ( oxidation half cell reaction ) is Correct, because Standard reduction potential of Chromium is - 0.74 V (i.e. E⁰_Cr+3/Cr = - 0.74 V) which is more negative than standard reduction potential of Cd (i.e. E⁰_Cd+2/Cd = - 0.40 V). Therefore Cr can reduce Cd as it is stronger reducing agent than Cd.

(3). Cd²⁺ is reduced at the cathode is Correct, because in Galvanic cell, reduction occurs at cathode while oxidation occurs at anode.

(4). As the cell runs, anions will migrate from the Cd²⁺|Cd compartment to the other compartment is Incorrect, because electrons will migrate from one compartment to the other compartment not ions.

(5). The cathode reaction is Cd -> Cd²⁺ + 2e^- is Incorrect, because in Galvanic cell, reduction occurs at cathode and reduction half cell reaction is : Cd²⁺ + 2e^- ---> Cd