Effect of temperature on the vapour pressure of a liquid is given by Clausius – Clapeyron equation.
ln(P2P1)=ΔHR(1T1−1T2)
where,
ΔH is the enthalpy of vapourisation=4.157×103 J mol−1P1 is the vapour pressure of the liquid at temperature T1=500 KP2 is the vapour pressure of the liquid at temperature T2=1000 K
Puting the values:
ln(P2150)=4.157×1038.314 J mol−1K−1×(1500−11000)
ln(P2150)=12
P2150=e 0.5P2=(1.65×150) torrP2=247.5 torr