Dichlorine monoxide, Cl₂O is sometimes used as a powerful chlorinating agent in research. It can be produced by passing chlorine gas over heated mercury (II) oxide according to the following equation:

HgO + Cl₂ → HgCl₂ + Cl₂O

What is the percent yield, if the quantity of the reactants is sufficient to produce 0.86g of Cl₂O but only 0.71 g is obtained?