When 3 g of carbon (C) reacts with 4 g of hydrogen gas (H_2) to produce methane (CH_4) according to the equation C + 2H_2 → CH_4, which reactant is the limiting reagent?

• A. Hydrogen gas (H_2)
• B. Methane (CH_4)
• C. Carbon (C)
• D. Both are limiting reagents

Answer: (A)

Verified step by step guidance

1. Write down the balanced chemical equation: \(\mathrm{C} + 2\mathrm{H}_2 \rightarrow \mathrm{CH}_4\).
2. Calculate the number of moles of each reactant using their molar masses: For carbon, \(\mathrm{moles} = \frac{3\,\mathrm{g}}{12.01\,\mathrm{g/mol}}\); for hydrogen gas, \(\mathrm{moles} = \frac{4\,\mathrm{g}}{2.02\,\mathrm{g/mol}}\).
3. Use the stoichiometric coefficients from the balanced equation to determine the mole ratio required for the reaction: 1 mole of C reacts with 2 moles of \(\mathrm{H}_2\).
4. Compare the actual mole ratio of \(\mathrm{H}_2\) to C with the required stoichiometric ratio to identify which reactant is in deficit.
5. The reactant that produces fewer moles of methane (based on stoichiometry) is the limiting reagent.