Tin(II) fluoride (stannous fluoride) is added to toothpaste as a convenient source of fluoride ion, which is known to help minimize tooth decay. The concentration of stannous fluoride in a particular toothpaste can be determined by precipitating the fluoride as the mixed salt PbClF.

Th e concentrations of Pb²⁺ and Cl^- are controlled so that PbCl₂ does not precipitate. If a sample of toothpaste that weighs 10.50 g produces a PbClF precipitate that weighs 0.105 g, what is the mass percentage of SnF₂ in the toothpaste?

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SnF₂(aq) + 2Pb²+(aq) + 2Cl (aq) → 2PbClF(s) + Sn²+ (aq)