Water carried away by N2 gas = 36 - 34.80 = 1.20 g
As this water is carried away by 50 L of N2 gas, this means that volume occupied by water vapours = 50 L.
Thus, now we have n = 1.20/18 = 0.0667 mol, V = 50 L, T = 300 K, P = ?
Applying the gas equation, PV = nRT
= 0.03286 × 760 mm = 24.97 mm.