lf 28.0g nitrogen gas is reacted with 8.0g of hydrogen gas to form Ammonia, the limiting reactant among the two will be:
Correct answer: A. N2
- A. N2
- B. H2
- C. Both a & b
- D. None of them
Explanation
The balanced chemical equation for the formation of ammonia (NH3) is:N2 + 3H2 → 2NH3You start with 28.0 g of N2 and 8.0 g of H2. The molar mass of N2 is 28.0 g/mol, so you have 1 mole of N2. The molar mass of H2 is 2.0 g/mol, so you have 4 moles of H2.According to the balanced equation, 1 mole of N2 requires 3 moles of H2 to fully react. Since you have only 1 mole of N2 and 4 moles of H2, N2 will run out first, making it the limiting reactant. Therefore, the correct answer is Option A: N2.Option B is incorrect because there is excess H2 present. Option C is incorrect because only one reactant can be limiting. Option D is incorrect because there must be a limiting reactant in this scenario.
This question appeared on the ETEA MDCAT 2008 paper, which you can sit online with every answer explained.
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About Limiting and Excess Reactants
Limiting and excess reactants are identified from the balanced chemical equation and the available amounts of each substance. The limiting reactant determines the maximum product formed, while the excess reactant remains after completion, so questions require mole ratios, theoretical yield and sometimes percentage yield calculations.
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