Calculate K for Rearranged Equation

Question

The equilibrium constant, K_c, for the following reaction is 20.1 at 318 K.

2CH₂Cl₂(g) CH₄(g) + CCl₄(g)

Calculate K_c at this temperature for the following reaction:

CH₂Cl₂(g) 1/2CH₄(g) + 1/2CCl₄(g)

K_c = 

Answer 1

Whenever you divide an equation by 2, as is the case here, the K for the new reaction is the square root of the value of the original K. Also, if you double the coefficients, the new K is the square of the original.

2CH2Cl2 <==> CH4 + CCl4 K = 20.1

CH2Cl2 <==> 1/2 CH4 + 1/2 CCl4 K = √20.1 = 4.48