Free CART Stoichiometry Questions and Answers — Questions and Answers
Question 1: In the balanced chemical equation 2H₂ + O₂ → 2H₂O, how many moles of water are produced when 3 moles of hydrogen gas react completely?
- 1.5 moles
- 2 moles
- 3 moles (Correct answer)
- 6 moles
Correct answer: 3 moles
From the balanced chemical equation, 2 moles of H₂ produce 2 moles of H₂O, indicating a 1:1 mole ratio between hydrogen gas and water. Therefore, if 3 moles of hydrogen gas react completely, an equal amount, 3 moles, of water will be produced.
Question 2: Given the reaction: N₂ + 3H₂ → 2NH₃, how many moles of hydrogen gas are needed to produce 4 moles of ammonia?
- 6 moles (Correct answer)
- 4 moles
- 3 moles
- 12 moles
Correct answer: 6 moles
The balanced equation N₂ + 3H₂ → 2NH₃ shows that 3 moles of hydrogen gas are required to produce 2 moles of ammonia. To produce 4 moles of ammonia (double the amount), you would need double the amount of hydrogen, which is 6 moles.
Question 3: In the reaction: 4Fe + 3O₂ → 2Fe₂O₃, what is the mole ratio of iron (Fe) to ferric oxide (Fe₂O₃)?
- 1:1
- 2:3
- 4:3
- 4:2 (Correct answer)
Correct answer: 4:2
The mole ratio between two substances in a balanced chemical equation is determined by their respective stoichiometric coefficients. For iron (Fe) and ferric oxide (Fe₂O₃) in the given reaction, the coefficients are 4 and 2, establishing a mole ratio of 4:2.
Question 4: How many grams of CO₂ are produced when 44 grams of propane (C₃H₈) undergo complete combustion according to the equation: C₃H₈ + 5O₂ → 3CO₂ + 4H₂O? (Molar masses: C₃H₈ = 44 g/mol, CO₂ = 44 g/mol)
- 44 grams
- 88 grams
- 132 grams (Correct answer)
- 176 grams
Correct answer: 132 grams
To solve this, we first convert the given mass of propane (C₃H₈) to moles using its molar mass (44 g/mol), which gives 1 mole of C₃H₈. According to the balanced chemical equation, 1 mole of C₃H₈ produces 3 moles of CO₂. Therefore, 1 mole of propane will produce 3 moles of CO₂. Finally, we convert these 3 moles of CO₂ back to grams using its molar mass (44 g/mol), resulting in 3 * 44 = 132 grams of CO₂.
Question 5: If 8 moles of Al react with 3 moles of Fe₂O₃ according to the equation: 2Al + Fe₂O₃ → 2Fe + Al₂O₃, what is the limiting reactant?
- Al
- Fe₂O₃ (Correct answer)
- Fe
- Al₂O₃
Correct answer: Fe₂O₃
The limiting reactant is the one that is completely consumed first, thereby stopping the reaction. From the balanced equation, 2 moles of Al react with 1 mole of Fe₂O₃. If we have 8 moles of Al, it would require 8/2 = 4 moles of Fe₂O₃ to react completely. Since only 3 moles of Fe₂O₃ are available, which is less than the 4 moles needed, Fe₂O₃ will run out first and is therefore the limiting reactant.
Free CART Stoichiometry Questions and Answers
In the balanced chemical equation 2H₂ + O₂ → 2H₂O, how many moles of water are produced when 3 moles of hydrogen gas react completely?