Question

a pressure of 96.5Kpa is exerted by a mixture of nitrogen gas and water vapor in a equilibrium with liquid water at 18 degree celcius , what is the partial pressure exerted by the nitrogen gas?

Answer 1

Look up the vapor pressure of H2O at 18 C. This is the partial pressure of H2O at that T.
Ptotal = pN2 + pH2O.
You know Ptotal and pH2O. Solve for pN2.