Free RPAL Stoichiometry Questions and Answers — Questions and Answers
Question 1: What does stoichiometry primarily deal with in a chemical reaction?
- The speed of the reaction
- The energy released during the reaction
- The quantitative relationships between reactants and products (Correct answer)
- The color change in the reaction
Correct answer: The quantitative relationships between reactants and products
Stoichiometry involves calculating the quantities of reactants and products in a chemical reaction based on a balanced chemical equation.
Question 2: In the balanced equation 2H₂ + O₂ → 2H₂O, how many moles of water are produced from 3 moles of oxygen?
- 3 moles
- 6 moles (Correct answer)
- 4 moles
- 2 moles
Correct answer: 6 moles
The balanced equation shows that 1 mole of O₂ produces 2 moles of H₂O. Therefore, 3 moles of O₂ will produce 6 moles of H₂O.
Question 3: What is the mole ratio of aluminum (Al) to aluminum oxide (Al₂O₃) in the reaction 4Al + 3O₂ → 2Al₂O₃?
- 2:3
- 3:4
- 4:2 (Correct answer)
- 1:1
Correct answer: 4:2
The balanced equation shows a mole ratio of 4 moles of Al to 2 moles of Al₂O₃, which simplifies to a ratio of 2:1.
Question 4: In the reaction 2Na + Cl₂ → 2NaCl, how many grams of NaCl can be produced from 46 grams of Na (atomic mass of Na = 23 g/mol)?
- 23 grams
- 46 grams
- 92 grams (Correct answer)
- 184 grams
Correct answer: 92 grams
46 grams of Na corresponds to 2 moles (since 23 g/mol * 2 = 46 g). According to the stoichiometry of the reaction, 2 moles of Na produce 2 moles of NaCl, which has a molar mass of 58.5 g/mol. Thus, 2 moles of NaCl weigh 2 * 58.5 g = 117 g.
Question 5: If you have 10 grams of H₂ and 80 grams of O₂, which is the limiting reactant in the reaction 2H₂ + O₂ → 2H₂O?
- H₂ (Correct answer)
- O₂
- H₂O
- None, they are in perfect ratio
Correct answer: H₂
10 grams of H₂ corresponds to 5 moles (H₂ has a molar mass of 2 g/mol), and 80 grams of O₂ corresponds to 2.5 moles (O₂ has a molar mass of 32 g/mol). According to the equation, 2 moles of H₂ are required for every 1 mole of O₂, so H₂ is the limiting reactant.
Free RPAL Stoichiometry Questions and Answers
What does stoichiometry primarily deal with in a chemical reaction?