How many grams of magnesium metal will react completely with 5.2 liters of 4.0 M HCl?

Mg (s) + 2 HCl (aq) - - > MgCl2 (aq) + H2 (g)

1) Find the number of mols of HCl in 5.2 liters of 4.0M solution:

n = M*V (L) = 4.0 mol/L * 5.2 L = 20.8 mol

2) Find the number of mols of Mg that will react with 20.8 mol of HCl, using the coefficients of the balanced equation

[1mol Mg / 2 mol HCl] * 20.8 mol HCl = 10.4 mol Mg

3) Transform mol to mass using the atomic mass:

10.4 mol Mg * 24.3 g/mol = 252.7 g of Mg.