Hey everyone! I need help solving this problem:

 

At 373 K, a reaction for the production of chlorine gas is

 

4HCl (g) + O2 (g) <-> 2H2O (g) + 2Cl2 (g)

K= 1.96 x 10^9

 

PHCl= 0.5 atm

PO2= 0.1 atm

PH20= 0.1 atm

PCl2= 0.2 atm

 

I know I have to start with doing a completion table so:

 

   4HCl (g) + O2 (g) <-> 2H2O (g) + 2Cl2 (g)

 I   0.5            0.1              0.1              0.2    

C  

comp.

 

But the problem is that I'm not sure how to determine what the change is. The answer reads as follows:

 

  4HCl (g) + O2 (g) <-> 2H2O (g) + 2Cl2 (g)