Electrochemistry Extra Practice Question

(a)(ii) To consider the effect of CO₂ on the cathode reaction, identify the half-equation from Data Booklet to be considered at cathode? (You may find consider equation (1) of the question useful)

• O₂ + 2H₂O + 4e⁻ ⇌  4OH⁻

• O₂ + 4H⁺ + 4e⁻ ⇌  2H₂O

• O₂ + 2H⁺ + 2e⁻ ⇌  H₂O₂

• O₂ + H₂O + 2e⁻ ⇌  HO₂⁻ + OH⁻

(a)(ii) After identifying the half-equation from Data Booklet to be considered at cathode (see below),

O₂ + 2H₂O + 4e⁻ ⇌  4OH⁻

How would the presence of atmospheric CO₂ affects E_cathode? (You may need to refer to equation (2) in the question)

• more positive

• less positive

(a)(ii) To consider the effect of CO₂ on the anode reaction, identify the half-equation from Data Booklet to be considered at anode? (You may find consider equation (3) of the question useful)

• H₂ ⇌ 2H⁺ + 2e⁻

• 2H⁺ + 2e⁻ ⇌ H₂

• 2H₂O + 2e⁻ ⇌  H₂ + 2OH⁻

• H₂ + 2OH⁻ ⇌  2H₂O + 2e⁻

(a)(ii) After identifying the half-equation from Data Booklet to be considered at anode (see below),

2H⁺ + 2e⁻ ⇌ H₂

How would the presence of CO₃²⁻ (which migrates from the cathode) affects E_anode?

(You may need to refer to equation (4) in the question)

• less negative

• more negative

(a)(ii) By considering the effect on E_cathode and E_anode (from previous questions) and also with the use of a suitable equation, how the E_cell of the EDCS changes?

• less positive

• more positive

(b)(i) To consider the E_cell of a typical hydrogen-oxygen fuel cell under acidic condition, we need to identify the correct half-equation at both the cathode and the anode under acidic conditions.

Which of the following is the correct half-equation to be considered at the cathode?

• O₂ + 2H₂O + 4e⁻ ⇌  4OH⁻

• O₂ + 4H⁺ + 4e⁻ ⇌  2H₂O

• O₂ + 2H⁺ + 2e⁻ ⇌  H₂O₂

• O₂ + H₂O + 2e⁻ ⇌  HO₂⁻ + OH⁻

(b)(i) To consider the E_cell of a typical hydrogen-oxygen fuel cell under acidic condition, we need to identify the correct half-equation at both the cathode and the anode under acidic conditions.

Which of the following is the correct half-equation to be considered at the anode?

• H₂ ⇌ 2H⁺ + 2e⁻

• 2H⁺ + 2e⁻ ⇌ H₂

• 2H₂O + 2e⁻ ⇌  H₂ + 2OH⁻

• H₂ + 2OH⁻ ⇌  2H₂O + 2e⁻

(b)(i) By considering the E_cathode and E_anode (from previous questions) and also with the use of a suitable equation, calculate E_cell of a typical hydrogen-oxygen fuel cell under acidic condition?

• +1.23 V

• −1.23 V

(b)(i) To consider the E_cell of a typical hydrogen-oxygen fuel cell under alkaline condition, we need to identify the correct half-equation at both the cathode and the anode under alkaline conditions.

Which of the following is the correct half-equation to be considered at the cathode?

• O₂ + 2H₂O + 4e⁻ ⇌  4OH⁻

• O₂ + 4H⁺ + 4e⁻ ⇌  2H₂O

• O₂ + 2H⁺ + 2e⁻ ⇌  H₂O₂

• O₂ + H₂O + 2e⁻ ⇌  HO₂⁻ + OH⁻

(b)(i) To consider the E_cell of a typical hydrogen-oxygen fuel cell under alkaline condition, we need to identify the correct half-equation at both the cathode and the anode under alkaline conditions.

Which of the following is the correct half-equation to be considered at the anode?

• H₂ ⇌ 2H⁺ + 2e⁻

• 2H⁺ + 2e⁻ ⇌ H₂

• 2H₂O + 2e⁻ ⇌  H₂ + 2OH⁻

• H₂ + 2OH⁻ ⇌  2H₂O + 2e⁻