Question

Boiling point of water at $750mmHg$ is ${99.63}^{\circ }C$. How much sucrose is to be added to $500g$ of water such that it boils at ${100}^{\circ }C$.

Answer 1

Given, $△T_b=100-99.63={0.37}^o;K_b=0.52$

Mass of water $=500g$

Let $xgm$ of sucrose be added.

Molar mass of sucrose $=342gmo{l}^{-1}$

Molality $\left(M\right)=\frac{x\times 1000}{342\times 500}=\frac{x}{171}$

$△T_b=K_b\times m$

$0.37=0.52\times \frac{x}{171}$

$x=121.67gm$

Therefore, $121.67gm$ of sucrose must be added.