A 15mg strip of Magnesium metal reacts in 5.0 mL of 1.0M HCl over a given period. Evaluate the (mol HCl)/(mol Mg) ratio for the reaction. moles of each Mg and HCl by using their masses?

First convert mass to grams: 15 mg = 0.015 g

n(Mg) = 0.015 g / 24.31 g-mol = 0.00062 mol

For HCl, determine from product of volume (in liters) and molarity:

n(HCl) = (0.005 L)(1.0 M) = 0.0050 mol

So the ratio (mol HCl/mol Mg) = 0.0050 / 0.00062 = 250 / 31