Stoichiometry Quiz

Grade 11 · Science · Quiz

10 questions covering mole calculations, balanced equations, limiting reagents, and percent yield.

Questions

1. What does Avogadro's number represent?

   1. The number of protons in a mole
   2. 6.022 × 10²³ particles per mole
   3. The molar mass of any element
   4. The charge on one mole of electrons
   Show answer

   Answer: 6.022 × 10²³ particles per mole

   Avogadro's number is the number of representative particles in exactly one mole of a substance.

2. Balance: _Fe + _O₂ → _Fe₂O₃. What are the coefficients?

   1. 1, 1, 1
   2. 2, 3, 2
   3. 4, 3, 2
   4. 3, 2, 2
   Show answer

   Answer: 4, 3, 2

   4Fe + 3O₂ → 2Fe₂O₃ balances 4 Fe atoms and 6 O atoms on each side.

3. How many moles are in 36.04 g of water (molar mass 18.02 g/mol)?

   1. 0.5 mol
   2. 1.0 mol
   3. 2.0 mol
   4. 4.0 mol
   Show answer

   Answer: 2.0 mol

   36.04 ÷ 18.02 = 2.0 mol.

4. In 2SO₂ + O₂ → 2SO₃, with 4 mol SO₂ and 1 mol O₂ available, which is limiting?

   1. SO₂
   2. O₂
   3. SO₃
   4. Neither
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   Answer: O₂

   4 mol SO₂ needs 2 mol O₂, but only 1 mol is available — O₂ is limiting.

5. What mass of CO₂ (44.01 g/mol) forms from complete combustion of 1 mol CH₄? (CH₄ + 2O₂ → CO₂ + 2H₂O)

   1. 16.05 g
   2. 28.01 g
   3. 44.01 g
   4. 88.02 g
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   Answer: 44.01 g

   1:1 mole ratio of CH₄ to CO₂ means 1 mol CH₄ → 1 mol CO₂ = 44.01 g.

6. Theoretical yield 8.0 g, actual yield 6.4 g. What is percent yield?

   1. 70%
   2. 75%
   3. 80%
   4. 85%
   Show answer

   Answer: 80%

   (6.4 / 8.0) × 100 = 80%.

7. How many grams are in 3.0 mol of NaCl (molar mass 58.44 g/mol)?

   1. 19.48 g
   2. 58.44 g
   3. 116.88 g
   4. 175.32 g
   Show answer

   Answer: 175.32 g

   3.0 mol × 58.44 g/mol = 175.32 g.

8. Which quantity is NOT needed for a mass-to-mass stoichiometric calculation?

   1. A balanced chemical equation
   2. Molar masses of reactants/products
   3. The temperature of the reaction
   4. The given mass of the starting material
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   Answer: The temperature of the reaction

   Temperature is not required for mass-to-mass stoichiometry — you need the equation, molar masses, and given mass.

9. At STP, what volume does 2.0 mol of ideal gas occupy?

   1. 11.2 L
   2. 22.4 L
   3. 33.6 L
   4. 44.8 L
   Show answer

   Answer: 44.8 L

   At STP, 1 mol ideal gas = 22.4 L. So 2.0 mol × 22.4 = 44.8 L.

10. In 5A → 3B, how many moles of B form from 15.0 mol of A?

    1. 3.0 mol
    2. 5.0 mol
    3. 9.0 mol
    4. 25.0 mol
    Show answer

    Answer: 9.0 mol

    15.0 mol A × (3 mol B / 5 mol A) = 9.0 mol B.

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