Question

In an experiment, 1 mol kcl is dissolved in a 1.4-kg sample of water, then 1 mol glucose is dissolved in another 1.4-kg sample of water. why does the kcl solution have the higher boiling point?

Answer 1

Answer:This is because the KCl van'T Hoff factor is greater than the van'T Hoff factor of glucose in water.

Step-by-step explanation:

van't Hoff factor of KCl =
`i_k` =2

van't Hoff factor of glucose=
`i_g` =1

Elevation in boiling point is given by:

`\Delta T_b=i* K_b* \frac{\text{Number of moles of compound}}{\text{Mass of solvent in kg}}`

`\Delta T_b\propto i`

Mass of the water and
`K_b` are same in both solution ,
`\Delta T_b` will depend upon van't Hoff factor of the compound.

• Higher the Van't Hoff number more will be the elevation in boiling point of the solution.
• Lower the Van'T Hoff number lessor will be elevation is boiling point of the solution.

Since,
`i_k>i_g` which means solution with KCl has more elevation is boiling point than the solution glucose.

Answer 2

Because presence of non-volatile substances (salt-KCl) decreases its mole fraction and the solution's volatility (tendency of a substance to vaporize) and in that way raises the normal boiling point in proportion to the concentration of the solutes (KCl). This is called boiling point elevation (solution has a higher boiling point than a pure solvent). Example is salt water (boils at a higher temperature than pure water).