Question

At 700 K, CCl4 decomposes to carbon and chlorine. The Kp value for the decomposition is 0.76. Find the starting pressure of CCl4 at this temperature that produces a total pressure of 1.9 atm at equilibrium.

Answer 1

The decomposition of CCl4 is as follows:

CCl4 (g) ---> C(s) + 2Cl2 (g) Kp = 0.76

where Kp = (PCl2)^2 / (P_CCl4)

P_C is zero since carbon is in solid form.

Express P_CCl4 in terms of P_Cl2

0.76 = (P_Cl2)^2 / (P_CCl4)

0.76P_CCl4 = (P_Cl2)^2

Ptotal = P_Cl2 = 1.9 atm

Solve for P_CCl4

P_CCl4 = 4.75 atm