A sample of impure tin of mass 0.520g is dissolved in strong acid to give a solution of Sn2+. The solution is...

A sample of impure tin of mass 0.520g is dissolved in strong acid to give a solution of Sn2+. The solution is then titrated with a 0.0448 M solution of NO3−, which is reduced to NO(g). The equivalence point is reached upon the addition of 3.79×10⁻²L of the NO3− solution.

Find the percent by mass of tin in the original sample, assuming that it contains no other reducing agents.