For which of the following reactions is the ratio kp/kc largest at 300 k?

Below are the choices:

A. Ni (CO) 4 (g) ⇌ Ni (s) + 4CO (g)

B. C (s) + 2H2 (g) ⇌ CH4 (g)

C. CaCO3 (s) ⇌ CaO (s) + CO2 (g)

D. N2 (g) + O2 (g) ⇌ 2 NO (g)

The answer is A. Ni (CO) 4 (g) ⇌ Ni (s) + 4CO (g)

The Kp/Kc ratio is equal to (RT) Δn. K is a constant and the temperature is held constant. So, the Kp/Kc ratio depends on Δn or the difference of moles of gaseous product and reactant. The reaction with the greatest Kp/Kc ratio is Ni (CO) 4 (g) ⇌ Ni (s) + 4CO (g) with a Δn of 3.