Kp=1.8×10−3kPa=1.8 Pa
T=700 K
We know that
Kp=Kc(RT)Δn
Kc=Kp(RT)Δn
R=8.314 J mol−1 K−1
Δn=(2+1)−2=1
Now put values;
Kc=1.8(8.314×700)1
Kc=3.09×10−7mol m−3