1. The problem statement, all variables and given/known data The reaction is PCl5 (g) <=> PCl3 (g) + Cl2 In an unknow volume, the following mixture is balanced: 0.14 atm of PCl5 0.36 atm of PCl3 0.50 atm of Cl2 What would be the the pressure of the whole mixture if the volume would be halved? (the answer is 1.88 atm) 2. Relevant equations p1+p2+p3=1 atm Kp=p3*p2/p1 3. The attempt at a solution Since the answer is 1.88 atm I assumed the ideal gas laws aren't valid in this question because then the pressure would be 2 atm. I calculated Kp and it's 1.29 atm. But now I'm stuck.