객관식
How many grams of aluminum (Al) must react with excess sulfuric acid (H_2SO_4) to produce 2.6 L of hydrogen gas (H_2) at STP?
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3. Chemical Reactions
Stoichiometry
객관식
When magnesium (Mg) reacts completely with excess hydrochloric acid (HCl), how many grams of hydrogen gas (H2) will be produced from 12 grams of Mg? (Reaction: Mg + 2HCl → MgCl2 + H2)
A
4.0 g
B
2.0 g
C
1.0 g
D
6.0 g
검증된 단계별 안내1
Write the balanced chemical equation for the reaction: \(\mathrm{Mg} + 2\mathrm{HCl} \rightarrow \mathrm{MgCl}_2 + \mathrm{H}_2\).
Calculate the number of moles of magnesium (Mg) used by dividing the given mass by the molar mass of Mg: \(\text{moles of Mg} = \frac{12\ \mathrm{g}}{24.305\ \mathrm{g/mol}}\).
Use the stoichiometry of the balanced equation to find the moles of hydrogen gas (\(\mathrm{H}_2\)) produced. According to the equation, 1 mole of Mg produces 1 mole of \(\mathrm{H}_2\), so moles of \(\mathrm{H}_2\) = moles of Mg.
Calculate the mass of hydrogen gas produced by multiplying the moles of \(\mathrm{H}_2\) by the molar mass of \(\mathrm{H}_2\) (2.016 g/mol): \(\text{mass of } \mathrm{H}_2 = \text{moles of } \mathrm{H}_2 \times 2.016\ \mathrm{g/mol}\).
The result from step 4 gives the mass of hydrogen gas produced from 12 grams of magnesium reacting completely with excess hydrochloric acid.
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