Identify the limiting reagent.

2.43g of magnesium is added to a solution containing 0.100 mol hydrochloric acid t ok produce hydrogen gas.

Mg + 2HCl ==>H2 + MgCl2

mols Mg = grams/molar mass
mols HCl = 0.100 mol

Using the coefficients in the balanced equation, convert mols Mg to mols H2.
Do the same for HCl.
In limiting reagent problems the limiting reagent is the one that produces the smaller mols of product.

To identify the limiting reagent in a chemical reaction, we need to compare the moles of the reactants.

First, let's convert the mass of magnesium to moles using its molar mass. The molar mass of magnesium is 24.31 g/mol.

Given:
Mass of magnesium = 2.43 g
Molar mass of magnesium = 24.31 g/mol

Number of moles of magnesium = mass of magnesium / molar mass of magnesium
Number of moles of magnesium = 2.43 g / 24.31 g/mol

Calculating this, we find:
Number of moles of magnesium = 0.100 mol

Now, let's compare the number of moles of magnesium to the number of moles of hydrochloric acid.

Given:
Number of moles of hydrochloric acid = 0.100 mol

From the balanced chemical equation, we know that the stoichiometric ratio between magnesium and hydrochloric acid is 1:2. This means that 1 mole of magnesium reacts with 2 moles of hydrochloric acid.

Since the ratio is 1:2, the number of moles of hydrochloric acid required for the reaction is twice the number of moles of magnesium.

Number of moles of hydrochloric acid required = 2 * number of moles of magnesium
Number of moles of hydrochloric acid required = 2 * 0.100 mol

Calculating this, we find:
Number of moles of hydrochloric acid required = 0.200 mol

We can see that the actual number of moles of hydrochloric acid (0.100 mol) is less than the number required (0.200 mol). Therefore, the hydrochloric acid is the limiting reagent in this reaction.