Zn(s) + 2HCl(aq) --> ZnCl2(aq) + H2(g) From the balanced chemical equation, 2 moles of HCl is required to react with 1 mole of Zn Mass of Zn = 9.55 g Molar mass of Zinc = 65.41 g/mol Number of moles = mass / molar mass Moles of Zn = 9.55 / 65.41 = 0.146 mol Moles of HCl required = 2 x moles of Zn = 2 x 0.146 = 0.292 mol