Verified Solution • 2025–26 Session moderate

QJEEM21Ch5cdd: JEE Main 2021 Chemistry - Class 11 JEEM21Ch5cdd Solution: The gas phase reaction at 400 K has G o = + 25.2 kJ mol -1 .…

The gas phase reaction 2A(g)⇌A2(g)2A(g) \rightleftharpoons {A_2}(g) at 400 K has Δ\Delta Go = + 25.2 kJ mol-1.

The equilibrium constant KC for this reaction is ________ ×\times 10 −- 2. (Round off to the Nearest Integer).

[Use : R = 8.3 J mol −- 1 K −- 1, ln 10 = 2.3 log10 2 = 0.30, 1 atm = 1 bar]

[antilog ( −- 0.3) = 0.501]

Step-by-Step Verified Solution

Using formula,

Δ\Delta G ∘^\circ = −- RTln(Kp)

⇒\Rightarrow 25.2 ×\times 103 = −- 8.3 ×\times 400 ×\times 2.3 log (Kp)

⇒\Rightarrow Kp = 10 −- 3.3

= 10 −- 3 ×\times 0.501

= 5.01 ×\times 10 −- 4 Bar −- 1

Also,

KpKc=(RT)Δng{{{K_p}} \over {{K_c}}} = {(RT)^{\Delta {n_g}}}

⇒KpKc=(RT)−1\Rightarrow {{{K_p}} \over {{K_c}}} = {(RT)^{ - 1}}

⇒Kc=Kp(RT)\Rightarrow {K_c} = {K_p}(RT)

=5.01×10−4×8.3×400= 5.01 \times {10^{ - 4}} \times 8.3 \times 400

=1.66×10−5= 1.66 \times {10^{ - 5}} m3/mole

=1.66×10−2= 1.66 \times {10^{ - 2}} L/mol

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