Assume that the decomposition of HNO3 can be represented by the following equation 4HNO3(g)⇌4NO2(g)+2H2O(g)+O2(g) and the reaction approaches equilibrium at 400K temperature and 30 atm pressure. At equilibrium partial pressure of HNO3 is 2atm. Calculate Kc at 400K : (Use R= 0.08 Latm/molK)
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Solution
We know, Ptotal=PHNO3+PNO2+PH2O+PO2 From the equation, PNO2=4PO2 PH2O=2PO2 So, Ptotal=PHNO3+7PO2 ⇒30−2=7PO2 ⇒PO2=4atm We have, Kp=P4NO2.P2H2O.PO2P4HNO3 ⇒Kp=(4×4)4×(2×4)2×424=220 We know, Kp=Kc(RT)Δng ⇒Kc=220323=32