When hydrochloric acid reacts with magnesium metal, hydrogen gas and aqueous magnesium chloride are produced. What volume of 9.0 M HCl is required to react completely with 5.00 g of magnesium?

Answer 1

Mg + 2HCl ==> H2 + MgCl2

Convert 5.00 g Mg to moles. moles = grams/molar mass

Using the coefficients in the balanced equation, convert moles Mg to moles HCl.

You know moles HCl = M x L.
You moles and M, solve for L.