Calculate Kc for the reaction.

Question

Consider the following equilibrium at 295 K:

NH_4HS(s)>>NH_3(g)+H_2S(g)

The partial pressure of each gas is 0.265 atm. Calculate Kc for the

reaction.

Answer 1

NH₄HS(s) ==> NH₃(g) + H₂S(g)

Kp = (P_NH3)(P_H2S) = (0.265)(0.265)

Kp = 0.0702

We can convert Kp to Kc as follows:

Kp = Kc(RT)^∆n where R = gas constant; T = temp in Kelvin and ∆n = change in # moles of gas

Kp = 0.0702

R = 0.0821 Latm/Kmol

T = 295K

∆n = 2

0.0702 = Kc(0.0821 * 295)²

0.0702 = Kc(587)

Kc = 1.20x10^-4

(be sure to check all of the math)