What mass of copper is consumed in the reaction with hydrochloric acid if 10.0 g of gas is collected?

317 g

Explanation:

Cu + 2HCl - -> CuCl2 + H2

1 : 2 1 : 1

1 mole of Cu = 63.5 g

1 mole of H2 = 2g

1 mole Cu produces = 1 mole of H2

63.5 g of Cu produces = 2 g of H2

So

10 g of H2 will be produced from = (63.5/2) * 10 = 317 g of Copper