Question

The molal elevation constant refers to which elevation in boiling point?

Answer 1

Elevation of boiling point:

• Let ${T_{\mathrm{b}}}^0$ be the boiling point of pure solvent and $T_{\mathrm{b}}$ be the boiling point of the solution.
• The increase in the boiling point $∆T_{\mathrm{b}}\mathit{=}{T}_{\mathit{b}}\mathit{-}{T_{\mathit{b}}}^{\mathit{0}}$is known as the elevation of the boiling point.
• "The elevation of boiling point $\left(∆T_{\mathrm{b}}\right)$ is directly proportional to the molal concentration of the solute in a solution." The expression can be given as:

$$\begin{gathered} ∆T_{\mathrm{b}}\mathit{\propto }\mathrm{m} \\ \mathrm{or}{T}_{\mathrm{b}}\mathit{=}{K}_{\mathrm{b}}\mathit{.}\mathrm{m} \end{gathered}$$

• where $\mathrm{m}$ is the molality and $K_{\mathrm{b}}$ is the boiling point elevation constant or molal elevation constant.

Units of molal elevation constant:

• It is expressed in $\mathrm{K}\mathrm{kg}{\mathrm{mol}}^{-1}$.

The molal elevation constant is the elevation in boiling point produced on dissolving one-mole solute in $1000\mathrm{g}$ of solvent.