Solutions - Intext Questions and Answer - class 12 chemistry

Solution:

Weight of Urea (W_B ) = 50 g

Molar mass (M_B ) of Urea (NH₂ CONH ₂) = 14 + 1 x 2 + 12 +16 +14 + 1 x 2 = 60 g mol ^{– 1}

Weight of water (W _A) = 850 g

Molar mass of water (M _A) = 18 g mol ^{– 1}

Vapour pressure of water (P _A ^o) = 23.8 mm Hg

Vapour pressure of water in the given solution P _A = ?

Now, number of moles of urea

Now, number of moles of water

Now, Mole fraction of urea

Now, we know that,

Thus, vapour pressure of water in this solution is 23.40 mm of Hg and its relative lowering is 0.017