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

Question

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

surry99 · Answer

Start with a balanced chemical equation and then set up your ICE table

cuanchi · Answer

This is not an easy problem
you have to do a system of 2 equations with 2 unknowns
1)  is the Kp = 0.76
the other is the total pressure 
2) Pt= 1.9 atm = Pccl4 + Pc + Pcl2

if you do the ICE table you will find the pressures at the equilibrium in function of the initial pressure
CCl4 -> C + 2 Cl2        Kp= Pc (Pcl2)^2 /Pccl4

Pccl4 = P-x
Pc= x
Pcl2= 2x

you can replace these values in the equation 2 and isolate P

3) P= 1.9/ (2x)

replace P in the equilibrium formula for 1.9/(2x) and solve for x

when you get the value of x, then go back to equation 3 to calculate initial P


I got this values
Initial P for CCl4=1.6284 atm
P of C at equilibrium = 0.5834
P of Cl at equilibrium = 1.1668
P of CCl4 at equilibrium = 1.045