(a) Explain the following: (i) Henry's law about the dissolution of a gas in a liquid. (ii) Boiling point elevation constant for a solvent. (b) A solution of glycerol (C3H8O3) in water was prepared by dissolving some glycerol in 500 g of water. This solution has a boiling point of 100.42 °C. What mass of glycerol was dissolved to make this solution?

Henry's law states that the partial pressure of a gas in the vapor phase is proportional to the mole fraction of the gas in the solution. If p is the partial pressure of the gas in the vapor phase and x is the mole fraction of the gas, then Henry's law can be expressed as: p = KHx where, KH is Henry's law constant.

(ii) The boiling point elevation constant or molal elevation constant is a constant quality for a solute which is related to molar mass and elevation in boiling point by the following relation:
Kb = ΔTb × MB × WA / WB × 1000
Where, Kb is the boiling point elevation constant
MB is the molar mass of the solute
WB is the weight of the solute
WA is the weight of the solvent
ΔTb is the elevation in boiling point

(b) WB = ?
WA = 500g
Kb = 0.512 K kg/mol
ΔTb = 100.42 °C - 100 °C = 0.42 °C
MB = 3 × 12 + 8 × 1 + 3 × 16 = 36 + 8 + 48 = 92

ΔTb = Kb × WB × 1000 / MB × WA
0.42 = 0.512 × WB × 1000 / 92 × 500
0.42 × 92 × 500 / 0.512 × 1000 = WB
WB = 37.33g