How many moles of H2 can be formed if a 2.97 g sample of Mg reacts with excess HCl?

The number of moles of H₂ formed when 2.97 g sample of Mg reacts with excess HCl is 0.122 moles

To determine the number of moles of H₂ that can be formed if 2.97 g sample of Mg reacts with excess HCl,

First, we will write a balanced chemical equation for the reaction

Mg + 2HCl → MgCl₂ + H₂

From the reaction above,

It means that 1 mole of Mg will react with 2 moles of HCl to produce 1 mole of MgCl₂ and 1 mole of H₂

Now, we will determine the number of moles of Mg present in the given sample.

From the question,

Mass of Mg = 2.97 g

Using the formula

Molar mass of Mg = 24.305 g/mol

∴

Number of moles of Mg in the sample = 0.122 moles

Since, 1 mole of Mg will react with 2 moles of HCl to produce 1 mole of MgCl₂ and 1 mole of H₂

∴ 0.122 moles of Mg will react with excess HCl to produce 0.122 moles of  H₂

Hence, the number of moles of H₂ formed when 2.97 g sample of Mg reacts with excess HCl is 0.122 moles

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