The composition of hydrogen selenide (H2Se) can be determined by heating tin (Sn) in a measured volume of the gas. The hydrogen selenide is decomposed, producing solid tin selenide (SnSe) and hydrogen gas. If the temperature and pressure are unchanged, the gas volume when the decomposition is over is the same as it was to begin with.
Write a balanced chemical equation for the reaction between hydrogen selenide and tin (including physical states).
Explain briefly why your equation accounts for the fact that the gas volume is unchanged.
An easy to understand solution is provided with all mathematical steps.