In the lab, a student collects hydrogen gas over water in a gas measuring tube. The hydrogen gas is produced when a piece of magnesium metal reacts with excess hydrochloric acid. What is the mass in grams of hydrogen gas collected if 2.49 g of magnesium metal is consumed in the reaction?The molar mass of Mg is 24.305 g/mol. The molar mass of H2 is 2.016 g/mol.
Question
In the lab, a student collects hydrogen gas over water in a gas measuring tube. The hydrogen gas is produced when a piece of magnesium metal reacts with excess hydrochloric acid. What is the mass in grams of hydrogen gas collected if 2.49 g of magnesium metal is consumed in the reaction?The molar mass of Mg is 24.305 g/mol. The molar mass of H2 is 2.016 g/mol.
Solution
To solve this problem, we need to use stoichiometry, which is a section of chemistry that involves using relationships between reactants and/or products in a chemical reaction to determine desired quantitative data.
Here are the steps:
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Write down the balanced chemical equation for the reaction. The reaction between magnesium and hydrochloric acid is: Mg + 2HCl -> MgCl2 + H2
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Calculate the number of moles of magnesium. We can do this using the molar mass of magnesium. The molar mass of Mg is given as 24.305 g/mol. So, the number of moles of Mg = mass of Mg / molar mass of Mg = 2.49 g / 24.305 g/mol = 0.102 mol
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From the balanced chemical equation, we can see that the mole ratio of Mg to H2 is 1:1. This means that the number of moles of hydrogen gas produced is equal to the number of moles of magnesium reacted. So, the number of moles of H2 = 0.102 mol
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Finally, we can find the mass of hydrogen gas produced by multiplying the number of moles of H2 by the molar mass of H2. The molar mass of H2 is given as 2.016 g/mol. So, the mass of H2 = number of moles of H2 * molar mass of H2 = 0.102 mol * 2.016 g/mol = 0.206 g
So, the mass of hydrogen gas collected is 0.206 g.
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