If 4.00 g of Mg is reacted with 3.20 g of HCl, what is the limiting reactant?

The balanced reaction is Mg + 2HCl → MgCl₂ + H₂, so 1 mole of Mg requires 2 moles of HCl. The amounts are about 0.165 mol Mg (4.00 ÷ 24.3) and 0.0878 mol HCl (3.20 ÷ 36.46). The Mg would need about 0.330 mol HCl, but only 0.0878 mol is available, so HCl is the limiting reactant.

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