A sensitive test for bismuth(III) ion consists of shaking a solution suspected of containing the ion with

Question:

A sensitive test for bismuth(III) ion consists of shaking a solution suspected of containing the ion with a basic solution of sodium stannite, Na2SnO2. A positive test consists of the formation of a black precipitate of bismuth metal. Stannite ion is oxidized by bismuth(III) ion to stannate ion, SnO32. Write a balanced equation for the reaction.