At 1127 K and 1 atm pressure, a gaseous mixture of CO and CO2 in equilibrium with solid carbon has 90.55% CO by mass
C(s)+CO2(g)↔2CO(g)
Calculate Kc for this reaction at the above temperature.
Let the total mass of the gaseous mixture be 100 g.
Mass of CO=90.55 g
and, mass of CO2=(100−90.55)=9.45g
Now, number of moles of CO, nco=90.5528=3.234 mol
Number of moles of CO2., nco2=9.4544=0.215 mol
Particular pressure of CO, Pco=nconco+nco2×Ptotal=3.2343.234+0.215×1=0.938 atm
Partal pressure of CO2, Pco2=nconco+nco2×Ptotal=0.2153.234+0.215×1=0.062 atm
Therefore, Kp=[CO]2[CO2]=(0.938)20.062=14.19
For the given reaction, Δ n=2−1=1
We know that,
Kp=Kc(RT)Δ n⇒14.19=Kc(0.082×1127)1⇒Kc=14.190.082×1127=0.154(approximately)