Class 12th Chemistry 2017 Set3 Outside Delhi Board Paper Solution

Question 13

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

Eo_cell = 0.236 V at 298 K. Calculate the standard Gibbs energy of the cell reaction. (Given : 1F = 96,500 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 : 1F = 96,500 C mol-1)

Answer

(a) E0 cell = 0.236 V

∆Gθ = -NFEθ

n=2, F=96500C

∆G0 = 2 × (96500 C) × (0.236 V)

= -45548 J

= -45.55 KJ

∆Gθ = -2303 RT log KC

logK_c = ∆G0 / 2.303 RT

= - 45.55 / (2.303 × 8.314 × 10-3 × 298)

= 7.983

Kc = antilog (7.983)

= 9.62 × 107

(b) Current, I = 0.5 A

Time, t = 2 hours

In sec we get Time,

t = 2 × 60 × 60 s = 7200 s

Charge : Q = I × t

= 0.5 A × 7200 s

= 3600 Coulombs

Number of electrons = total charge / charge on 1 electrons

= 3600 / (1.6 × 1019)

= 2.25 × 1022 electrons