DAT General Chemistry: Stoichiometry 3 — Questions and Answers
Question 1: What volume does 1.0 mol of an ideal gas occupy at STP?
- 11.2 L
- 22.4 L (Correct answer)
- 24.5 L
- 1.0 L
Correct answer: 22.4 L
At STP one mole of any ideal gas occupies 22.4 L.
Question 2: If a reaction has a theoretical yield of 50 g and an actual yield of 40 g, what is the percent yield?
- 80% (Correct answer)
- 125%
- 90%
- 10%
Correct answer: 80%
Percent yield is actual/theoretical × 100 = 40/50 × 100 = 80%.
Question 3: How many moles of CO2 are produced from 1.5 mol of CaCO3 in CaCO3 → CaO + CO2?
- 1.5 mol (Correct answer)
- 3.0 mol
- 0.75 mol
- 1.0 mol
Correct answer: 1.5 mol
The 1:1 ratio means 1.5 mol CaCO3 yields 1.5 mol CO2.
Question 4: What is the molar mass of glucose, C6H12O6 (C=12, H=1, O=16)?
- 180 g/mol (Correct answer)
- 150 g/mol
- 120 g/mol
- 90 g/mol
Correct answer: 180 g/mol
6(12) + 12(1) + 6(16) = 72 + 12 + 96 = 180 g/mol.
Question 5: How many oxygen atoms are present in one formula unit of Al2(SO4)3?
- 4
- 7
- 12 (Correct answer)
- 9
Correct answer: 12
Three sulfate groups each with 4 oxygens give 3 × 4 = 12 oxygen atoms.
Question 6: A 0.25 mol sample of a gas weighs 11 g; what is its molar mass?
- 22 g/mol
- 44 g/mol (Correct answer)
- 2.75 g/mol
- 88 g/mol
Correct answer: 44 g/mol
Molar mass equals mass divided by moles: 11 g / 0.25 mol = 44 g/mol.
Question 7: How many moles of Cl atoms are in 2 mol of CCl4?
- 2 mol
- 4 mol
- 8 mol (Correct answer)
- 6 mol
Correct answer: 8 mol
Each CCl4 has 4 Cl atoms, so 2 mol contains 2 × 4 = 8 mol of Cl.
DAT General Chemistry: Stoichiometry 3
What volume does 1.0 mol of an ideal gas occupy at STP?