A student performs an experiment to determine the volume of hydrogen gas produced when a given mass of magnesium reacts with excess HCl (aq), as represented by the net ionic equation below. The student begins with a 0.0360 g sample of pure magnesium and a solution of 2.0 M HCl (aq). (equation: Mg(s) + 2H+ (aq) --> Mg2+ (aq) + H2 (g))

a. Calculate the number of moles of HCl (aq) needed to react completely with the sample of magnesium.

b. Calculate the number of moles of HCl (aq) needed to react completely with the sample of magnesium.