Question

Suppose in an experiment to determine the amount of sodium hypochlorite in bleach, 0.0000552 mol KIO3 were titrated with an unknown solution of Na2S2O3 and the endpoint was reached after 17.80 mL

How many moles of Na2S2O3 did this require?

Answer 1

Here, the reaction is,

IO₃^- (aq) + 6S₂O₃^2- (aq) + 6H⁺ (aq)      $\rightarrow$        I^- (aq) + 3S₄O₆^2- (aq)

Moles of IO₃^- reacted = 0.0000552 moles

One mole of IO₃^- require six moles of Na₂S₂O₃

Therefore,

Moles of Na₂S₂O₃ required = 0.0000552 mol x 6 = 0.0003312 mol Na₂S₂O₃