Q.

A vessel at 1000 K contains CO2 with a pressure of 0.5 atm. Some of CO2 is converted into CO on addition of graphite. If total pressure at equilibrium is 0.8 atm, then Kp is:   [2025]

1 3 atm  
2 1.8 atm  
3 0.18 atm  
4 0.3 atm  

Ans.

(2)

CO2(g)+C(s)⟶2CO(g)t=00.5 atm00t=∞(0.5-p) atm0  2p atm

Total pressure at equilibrium=PCO2+PCO=0.5-p+2p=0.5+p=0.8, p=0.3 atm

Hence, PCO2=0.5-p=(0.5-0.3)=0.2 atm

PCO=2p=2×0.3=0.6 atm

Kp=PCO2PCO2=(0.6)20.2=1.8