JEE Main · 2022 · 26 Jun 2022 · Shift 2 · Chemical Thermodynamics

40%

of HI undergoes decomposition to

H_{2}

and

I_{2}

300 K

Δ G^{⊖}

for this decomposition reaction at one atmosphere pressure is

____

J mol^{- 1}

. [nearest integer]
(Use

R = 8.31 J K^{- 1} mol^{- 1}

;

lo g 2 = 0.3010

ln 10 = 2.3

lo g 3 = 0.477

)

Answer: 2735

Solution

For the reaction

HI ⇌ \frac{1}{2} H_{2} + \frac{1}{2} I_{2}

:

At equilibrium: HI = 0.6,

H_{2} = 0.2

I_{2} = 0.2

K_{p} = \frac{( 0.2 ) ^{1/2} ( 0.2 ) ^{1/2}}{0.6} = \frac{0.2}{0.6} = \frac{1}{3}

.

At equilibrium,

Δ G = 0

, so

Δ G^{\circ} = - R T ln K_{p}

Δ G^{\circ} = - 8.31 \times 300 \times 2.3 \times lo g (1/3) = - 8.31 \times 300 \times 2.3 \times (- 0.477) = 2735

J/mol.

JEE Main · 2022 · 26 Jun 2022 · Shift 2 · Integer answer