Quick! Chemistry help!?

Question

You react a metal with hydrochloric acid to produce hydrogen and a metal chloride.

How can you determine the empirical formula of the metal chloride from the ratio of the mass of the metal chloride to the mass of the metal?

(The masses have been determined by experiment)

Answer 1

Suppose the ratio is 1+r (we know it must be more than 1). If the atomic weight of the metal is M, then one mole of metal gives M g of metal and therefore M(1+r) = (M + Mr) g of metal chloride. M g of this will be the metal atoms, so (Mr) g will be the chloride. So one mole of metal bonds with (Mr / 35.5) moles of chlorine atoms, i.e. there are (Mr / 35.5) chlorine atoms for every metal atom.