Question

Suppose a student diluted and titrated a bleach unknown exactly as described in the experimental procedure, except only a single titration was performed which required 12.62 mL of 0.100 M Na_{2}S_{2}O_{3}

Calculate the number of moles of ClO in the sample titrated.

Answer 1

*The density of the original, undiluted bleach unknown was 1.042 g/mL.

Answer 2

This is a classic titration of hypochlorite in bleach. Usually done into a KI/ClO^- solution => I2 which is titrated with the S2O3^2- until all Red-Brown color is changed to clear solution. The ratio is 2 mole S2O3^2- to 1 mole ClO^-. So use Molarity x Volume in Liters => moles S2O3^2- used, then divide by 2 => moles of ClO^-.