NH4CN(s)⇌NH3(g)+HCN(g)
Pressure at equilibrium PP
∴ Total pressure at equilibrium, 2P=0.298
∴P=0.149atm
∴Kp=P′NH3×P′HCN
=0.149×0.149=0.0222atm2
If dissociation is made in presence of NH3 at 0.25 atm
NH4CN(s)⇌NH3(g)+HCN(g)
Initial pressure 00.25
Pressure at equilibrium (0.25+P′)P′
Also, Kp=P′(0.25+P′)
or 0.0222=P′(0.25+P′)
∴P′=0.0694atm