CBSE Class 12 · 2018 · Redox Reactions and ElectrochemistryShort Answer

(a) The cell in which the following reaction occurs:

2F e^{3 +} (aq) + 2 I^{-} (aq) ⟶ 2F e^{2 +} (aq) + I_{2} (s)

has

E_{ce l l}^{\circ} = 0.236

V at 298 K. Calculate the standard Gibbs energy of the cell reaction. (Given: 1 F = 96500 C mol

^{- 1}

)
(b) How many electrons flow through a metallic wire if a current of 0.5 A is passed for 2 hours? (Given 1 F = 96500 C mol

^{- 1}

)

Answer: (a) ΔG° ≈ −45.55 kJ mol⁻¹ (b) ≈ 2.25 × 10²² electrons

Solution

(a) Here

n = 2

Δ G^{\circ} = - n F E_{ce l l}^{\circ} = - 2 \times 96500 \times 0.236

Δ G^{\circ} = - 45548 J = - 45.55 kJ mo l^{- 1}

(b) Charge passed:

Q = I t = 0.5 \times 2 \times 3600 = 3600 C

Moles of electrons:

\frac{3600}{96500} = 0.0373 mol

Number of electrons:

0.0373 \times 6.022 \times 1 0^{23}

= 2.25 \times 1 0^{22} electrons

CBSE Class 12 Board · 2018 · Subjective