For a gas-phase reaction at 400 K, the ratio K_p/K_c is found to be about 1.08x10^3 (pressures in atm, concentrations in mol L^-1; R = 0.0821 L atm mol^-1 K^-1). Which of the following reactions could it be?

Fe2O3(s) + 3CO(g) 2Fe(s) + 3CO2(g)

JEE Advanced levelOne or more correct optionsDifficulty 3 of 3ce107

For a gas-phase reaction at 400 K, the ratio $K_{p} / K_{c}$ is found to be about $1.08 \times 1 0^{3}$ (pressures in atm, concentrations in $mol L^{- 1}$ ; $R = 0.0821 L atm mo l^{- 1} K^{- 1}$ ). Which of the following reactions could it be?

RT = 0.0821 \times 400 = 32.84

and

(RT)^{2} = 1078

, so

Δ n_{g a s} = + 2

. Counting gaseous species only: option 1 has

4 - 2 = + 2

, option 2 has

4 - 2 = + 2

, option 3 has

2 - 1 = + 1

(carbon is a solid) and option 4 has

3 - 3 = 0

. So options 1 and 2 fit.