Mg(s) + 2 HCl(aq) --> MgCl2(aq) + H2(g) how many moles of Mg are there? how many moles of hydrogen gas?

Answer 1

The balanced equation of Mg(s) + 2HCl(aq) ==> MgCl2(aq) + H2(g) does NOT tell you how many moles of Mg or H2 are present. It only tells you the MOLE RATIO of the reactants and products. Thus, 1 mole Mg reacts with 2 moles HCl to produce 1 mole of hydrogen gas.