What do you mean by the term 'elevation of boiling- point'?

1.	What do you mean by the term 'elevation of boiling- point'?
Answer» Similar to lowering of vapour pressure, the elevation of boiling point also depends on the number of solute molecules rather than their mixture. A solution of 1 mol of sucrose in 100 g of water boils at 373.52 K at one atmospheric pressure. Let T_b⁰ be the boiling point of pure solvent and T_b be the boiling point of solution. The increase in the boiling point ΔT_b = T_b - T_b⁰ is known as elevation of boiling point. Experiments have shown that for dilute solutions the elevation of boiling point (ΔT_b) is directly proportional to the molal concentration of the solute in a solution. Thus ΔT_b ∝ m or ΔT_b ∝ K_bm Here m(molality) is the number of moles of solute dissolved in 1 kg of solvent and the constant of proportionality K_b is called boiling point Elevation constant or molal Elevation Constant.

Answer»

Similar to lowering of vapour pressure, the elevation of boiling point also depends on the number of solute molecules rather than their mixture. A solution of 1 mol of sucrose in 100 g of water boils at 373.52 K at one atmospheric pressure.

Let T_b⁰ be the boiling point of pure solvent and T_b be the boiling point of solution. The increase in the boiling point ΔT_b = T_b - T_b⁰ is known as elevation of boiling point. Experiments have shown that for dilute solutions the elevation of boiling point (ΔT_b) is directly proportional to the molal concentration of the solute in a solution. Thus

ΔT_b ∝ m

or ΔT_b ∝ K_bm

Here m(molality) is the number of moles of solute dissolved in 1 kg of solvent and the constant of proportionality K_b is called boiling point Elevation constant or molal Elevation Constant.

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