homework question

Question

The equilibrium constant for the chemical equation

N2(g )+ 3H2(g)↽−−⇀ 2NH3(g) is 𝐾p=0.286 at 257∘C.

Calculate the value of 𝐾c or the reaction at 257 ∘C.

Answer 1

For this, you need to know (memorize) the following conversion:

Kp = Kc(RT)^∆n

Kp = 0.286

Kc = ?

R = gas constant = 0.0821 L-atm/K-mol

T = temperature in K = 257C + 273 = 530K

∆n = change in number of moles from reactant side to product side = 2 - 4 = -2 (note to keep the sign)

Solving the equation for Kc, we have

Kc = Kp / (RT)^∆n

Kc = 0.286 / (0.0821 * 530)^-2

Kc = 0.286 / 0.00053

Kc = 540