At 300 K, A -> B has Delta G deg = +20.0 kJ mol^-1 and B -> C has Delta G deg = -35.0 kJ mol^-1. The equilibrium constant of the overall reaction A -> C is about (use 2.303RT = 5.744 kJ mol^-1)

JEE Advanced levelSingle correct optionDifficulty 3 of 3td107

At $300 K$ , $A B$ has $Δ G^{\circ} = + 20.0 kJ mo l^{- 1}$ and $B C$ has $Δ G^{\circ} = - 35.0 kJ mo l^{- 1}$ . The equilibrium constant of the overall reaction $A C$ is about (use $2.303 RT = 5.744 kJ mo l^{- 1}$ )

Gibbs energies of consecutive steps add:

Δ G^{\circ} = 20.0 - 35.0 = - 15.0 kJ

(the equilibrium constants multiply,

K = K_{1} K_{2}

lo g_{10} K = 15.0/5.744 = 2.611

, so

K = 4.1 x 1 0^{2}

. The other options use only one step or add magnitudes.