The mass of a non-volatile solute of molar mass 60 ~g ~mol ⁻¹ that should be dissolved in 126 ~g of water to reduce its vapour pressure to 99 % will be

Step-by-step solution

Given, molar mass of solute, ₂=60 ~g / mol Mass of water (W₁ )=126 ~g ^ Molar mass of water (M₁ )=18 ~g / mol p_ Solution (p_ s )=0.99 p^ Relative lowering of vapour pressure p^ -p_ s p^ = W₂ M₂ M₁ W₁ p^ -0.99 p^ W₂ 18 = 0.1 p^ 60 126 = W₂ 18 p^ 60 126 60 126 18 100 =4.2 ~g