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Stoichiometry: Introduction Practice Tests

These Grade 10 Science practice tests introduce moles, Avogadro constant, molar mass, particle and mass conversions, balanced-equation mole ratios, limiting reactants, theoretical yield, percent yield, and empirical formulas.

Skills covered

  • Using the mole as a counting unit and applying Avogadro constant to particles and formula units
  • Calculating molar mass from chemical formulas and converting among grams, moles, and particles
  • Reading balanced-equation coefficients as mole ratios and solving introductory reaction-amount problems
  • Identifying limiting and excess reactants and calculating theoretical and percent yield
  • Using composition data to determine empirical and molecular formulas

How to use these practice tests

Write the balanced equation, identify the known and unknown units, and use dimensional analysis. Keep units visible, use molar mass for grams-to-moles conversion, and use coefficients only after the equation is balanced.

For more Grade 10 Science practice, return to the Grade 10 Science category.

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Grade 10 Stoichiometry Introduction Practice Tests

Practice Grade 10 Science questions about moles, Avogadro constant, molar mass, particle and mass conversions, mole ratios, limiting reactants, yield, and empirical formulas.

Choose the best answer. Track units through mole conversions, use balanced-equation ratios, calculate molar mass, and identify limiting or excess reactants.

10 Questions
0/10 Questions0 %
Correct 0
Incorrect 0
Unanswered 10
1. QuestionMultiple choice

What is the limiting reactant?

Please select an answer first.

Correct answer: A

The correct answer is The reactant that is consumed first and limits the amount of product formed.

  1. Identify the stoichiometric quantity: Determine whether the question asks about moles, particles, molar mass, a mole ratio, yield, or a limiting reactant.
  2. Set up the relationship: The limiting reactant determines the maximum theoretical amount of product.
  3. Check the units and result: The correct answer is The reactant that is consumed first and limits the amount of product formed.

The limiting reactant determines the maximum theoretical amount of product.

2. QuestionMultiple choice

What is an excess reactant?

Please select an answer first.

Correct answer: B

The correct answer is A reactant that remains after the limiting reactant is consumed.

  1. Identify the stoichiometric quantity: Determine whether the question asks about moles, particles, molar mass, a mole ratio, yield, or a limiting reactant.
  2. Set up the relationship: The excess reactant is present in more than the required stoichiometric amount.
  3. Check the units and result: The correct answer is A reactant that remains after the limiting reactant is consumed.

The excess reactant is present in more than the required stoichiometric amount.

3. QuestionMultiple choice

If 3.00 mol H₂ reacts with 1.00 mol O₂ in 2H₂ + O₂ → 2H₂O, what amount of water can form?

Please select an answer first.

Correct answer: C

The correct answer is 2.00 mol H₂O.

  1. Identify the stoichiometric quantity: Determine whether the question asks about moles, particles, molar mass, a mole ratio, yield, or a limiting reactant.
  2. Set up the relationship: One mole O₂ requires two moles H₂ and produces two moles H₂O, so oxygen limits the reaction at 2.00 mol water.
  3. Check the units and result: The correct answer is 2.00 mol H₂O.

One mole O₂ requires two moles H₂ and produces two moles H₂O, so oxygen limits the reaction at 2.00 mol water.

4. QuestionMultiple choice

If 4.00 mol H₂ reacts with 1.00 mol O₂ in 2H₂ + O₂ → 2H₂O, which reactant limits the reaction?

Please select an answer first.

Correct answer: D

The correct answer is O₂.

  1. Identify the stoichiometric quantity: Determine whether the question asks about moles, particles, molar mass, a mole ratio, yield, or a limiting reactant.
  2. Set up the relationship: The available 1.00 mol O₂ requires exactly 2.00 mol H₂, leaving H₂ in excess.
  3. Check the units and result: The correct answer is O₂.

The available 1.00 mol O₂ requires exactly 2.00 mol H₂, leaving H₂ in excess.

5. QuestionMultiple choice

What is theoretical yield?

Please select an answer first.

Correct answer: A

The correct answer is The maximum product amount predicted by stoichiometry.

  1. Identify the stoichiometric quantity: Determine whether the question asks about moles, particles, molar mass, a mole ratio, yield, or a limiting reactant.
  2. Set up the relationship: Theoretical yield assumes the reaction proceeds completely with no experimental losses.
  3. Check the units and result: The correct answer is The maximum product amount predicted by stoichiometry.

Theoretical yield assumes the reaction proceeds completely with no experimental losses.

6. QuestionMultiple choice

How is percent yield calculated?

Please select an answer first.

Correct answer: B

The correct answer is Actual yield ÷ theoretical yield × 100%.

  1. Identify the stoichiometric quantity: Determine whether the question asks about moles, particles, molar mass, a mole ratio, yield, or a limiting reactant.
  2. Set up the relationship: Percent yield compares the product collected with the maximum predicted amount.
  3. Check the units and result: The correct answer is Actual yield ÷ theoretical yield × 100%.

Percent yield compares the product collected with the maximum predicted amount.

7. QuestionMultiple choice

A substance contains about 40.0% carbon, 6.7% hydrogen, and 53.3% oxygen. What empirical formula is most likely?

Please select an answer first.

Correct answer: C

The correct answer is CH₂O.

  1. Identify the stoichiometric quantity: Determine whether the question asks about moles, particles, molar mass, a mole ratio, yield, or a limiting reactant.
  2. Set up the relationship: Converting percentages to moles and simplifying the ratio gives approximately 1:2:1.
  3. Check the units and result: The correct answer is CH₂O.

Converting percentages to moles and simplifying the ratio gives approximately 1:2:1.

8. QuestionMultiple choice

If the empirical formula is CH₂O and the molecular molar mass is about 180 g/mol, what is the molecular formula?

Please select an answer first.

Correct answer: D

The correct answer is C₆H₁₂O₆.

  1. Identify the stoichiometric quantity: Determine whether the question asks about moles, particles, molar mass, a mole ratio, yield, or a limiting reactant.
  2. Set up the relationship: The empirical formula mass is about 30 g/mol, and 180 ÷ 30 = 6, so multiply every subscript by 6.
  3. Check the units and result: The correct answer is C₆H₁₂O₆.

The empirical formula mass is about 30 g/mol, and 180 ÷ 30 = 6, so multiply every subscript by 6.

9. QuestionMultiple choice

What should be compared to identify the limiting reactant?

Please select an answer first.

Correct answer: A

The correct answer is The available amount of each reactant with the amount required by the balanced mole ratio.

  1. Identify the stoichiometric quantity: Determine whether the question asks about moles, particles, molar mass, a mole ratio, yield, or a limiting reactant.
  2. Set up the relationship: Limiting-reactant analysis depends on stoichiometric amounts, not mass alone.
  3. Check the units and result: The correct answer is The available amount of each reactant with the amount required by the balanced mole ratio.

Limiting-reactant analysis depends on stoichiometric amounts, not mass alone.

10. QuestionMultiple choice

What is the first step in a mass-to-mass stoichiometry problem?

Please select an answer first.

Correct answer: B

The correct answer is Write or use a balanced chemical equation..

  1. Identify the stoichiometric quantity: Determine whether the question asks about moles, particles, molar mass, a mole ratio, yield, or a limiting reactant.
  2. Set up the relationship: The balanced equation provides the mole ratio needed to connect reactant and product amounts.
  3. Check the units and result: The correct answer is Write or use a balanced chemical equation..

The balanced equation provides the mole ratio needed to connect reactant and product amounts.

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