For the gaseous reaction 3H2+N2⇌2NH3, the equilibrium pressures of H2  and N2 is 0.4 atm and 0.8 atm respectively. The total pressure of the equilibrium system is 2.8 atm.  The value  of  Kp is

3H2+N2⇌2NH3                                     Given P=2.8  0.4       0.8            ?                                                    PNH3=2.8−(PH2+PN2)                                                                                             =2.8−1.2=1.6 Kp=1.6×1.6(0.8)×(0.4)3        =2×1.60.4×0.4×0.4        =2004=50 atm−2