Question

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?

Answer 1

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

Explanation:

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

`NaClO = (74.5g)/(mol)`

`5.00g * (NaClO)/(74.5g) approx 0.0671mol`

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

`(0.0671mol)/(.0950kg) approx 0.706m`

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

`95.0g * (H_2O)/(18.0g) approx 5.28mol`

`(0.0671mol)/(0.0671mol+5.28mol) approx 0.0126`