# A household chlorine bleach is a water solution that is 5.00% by mass sodium hypochlorite. What is the molality of the hypochlorite in the solution? What is the mole fraction of hypochlorite in the solution?

Sep 3, 2017

Approximately $0.706 m$, and $0.0126$, respectively.

#### Explanation:

This requires an assumption that there is 5g solute and 95g solvent in 100g solution. Going from this:

$N a C l O = \frac{74.5 g}{m o l}$

$5.00 g \cdot \frac{N a C l O}{74.5 g} \approx 0.0671 m o l$

a. Molality is moles of solute over kilograms of solvent; it's a temperature independent measure of solubility.

$\frac{0.0671 m o l}{.0950 k g} \approx 0.706 m$

b. Mole fraction is the ratio of moles of solvent or solute per total moles of components of the solution, thus:

$95.0 g \cdot \frac{{H}_{2} O}{18.0 g} \approx 5.28 m o l$

$\frac{0.0671 m o l}{0.0671 m o l + 5.28 m o l} \approx 0.0126$