Which of the following will increase the pressure of CH4​ ?

Question

Coal, which is primarily carbon, can be converted to natural gas, primarily CH4​, by the following exothermic reaction: C(s)+2H₂​(g)⇌CH₄​(g) Which of the following will increase the pressure of CH4​ ?

adding more C to the reaction mixture

adding more H2​ to the reaction mixture

raising the temperature of the reaction mixture

lowering the volume of the reaction mixture

adding a catalyst to the reaction mixture

adding neon gas to the reaction mixture 

Answer 1

C(s) + 2H₂​(g) ⇌ CH₄​(g) 

K_p, is the equilibrium constant in terms of pressure, is given by

K_p = (P_CH4)/(P_H2)² where P_CH4 = the pressure of CH₄ and P_H2 = the pressure of H₂

Note that C is not included in the equilibrium constant expression because it is a solid in a heterogeneous equilibrium.

The following will increase P_CH4, the pressure of CH₄

adding more H₂​ to the reaction mixture—since (P_CH4)/(P_H2)² is constant, raising P_H2 means raising P_CH4)

lowering the volume of the reaction mixture— PV = nRT. Lowering V means raising P

And raising P pushes equilibrium to the right where there are fewer gas molecules.

These things listed will not increase the pressure of CH₄

adding more C to the reaction mixture—no effect on P_CH4 because K_p does not depend on C

adding a catalyst to the reaction mixture—no effect on P_CH4 because catalyst does not affect K_p

adding neon gas to the reaction mixture—affects overall pressure, but not partial pressure of CH₄

This one I initially had as increasing the pressure of CH₄

raising the temperature of the reaction mixture—since PV = nRT, raising T means raising P

but, as correctly pointed out in the comment below, raising the temperature pushes equilibrium to the left (lower P_CH4 since the reaction is exothermic.)