Molar Ratio

Related Examples and Practice Problems

A worksheet titled 'Stoichiometry Worksheet 1 - Mole-to-Mole Calculations,' with instructions and chemical reaction problems related to stoichiometry, including questions about moles of aluminum oxide, oxygen, and water.
Chemistry mole ratio worksheet with questions on aluminum metal, hydrogen chloride, aluminum bromide, and sodium hydroxide reactions.
Worksheet titled 'Mole/Mole Ratio Problems' with four questions related to chemical reactions involving nitrogen and hydrogen, including reaction equations and space for answers.
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A worksheet titled 'Mole Ratio Worksheet' with sections for student name, date, and period. The worksheet contains two chemistry problems involving molar ratios from reaction equations, with blank spaces for answers.

Topic Summary & Highlights
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Core Concept

Mole ratio is the ratio of the moles of one substance to the moles of another substance in a balanced chemical equation. Mole ratios are essential in stoichiometry as they allow us to calculate the amounts of reactants and products involved in a chemical reaction.

Practice Tips

  • Memorize Common Ions: Focus on learning the common polyatomic ions, charges, and patterns.

  • Roman Numerals for Transition Metals: Practice associating transition metals with their possible charges.

  • Cross-Method for Formulas: To determine the correct formula, use the “criss-cross” method to balance charges between cations and anions.

Topic Overview Podcast

Check out our stoichiometry episodes that covers this topic.

Topic Related Resources

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Key Concepts

  1. Understanding Mole Ratio:

    • The mole ratio is determined from the coefficients in a balanced chemical equation.

    • These coefficients represent the number of moles of each reactant and product.

    • For example, in the reaction 2H₂ + O₂ → 2H₂O, the mole ratio of H₂ to O₂ is 2:1, and the mole ratio of H₂ to H₂O is 2:2, which simplifies to 1:1.

Example Problem: Using Mole Ratios in a Reaction

Problem: In the reaction below, how many moles of H2O\text{H}_2\text{O}H2​O are produced if 4.0 moles of O2\text{O}_2O2​ react completely?

$2\text{H}_2 + \text{O}_2 \rightarrow 2\text{H}_2\text{O}$

Solution:

  1. Write and Balance the Equation:

    • The equation is already balanced.

  2. Identify the Mole Ratio:

    • The mole ratio of O₂​ to H₂O is 1:2, as indicated by the coefficients.

  3. Set Up the Conversion:

    • To find the moles of H₂O from 4.0 moles of O₂, use the mole ratio:

      $4.0 \, \text{moles O}_2 \times \frac{2 \, \text{moles H}_2\text{O}}{1 \, \text{mole O}_2} = 8.0 \, \text{moles H}_2\text{O}$

Answer: 8.0 moles of H₂O are produced.

Video Resources

A woman during a video presentation about chemistry, with a blue overlay displaying the question about using a mole to mole ratio, and she is speaking with her hand gestures.
A person holding a whiteboard with the handwritten text 'Stoichiometry: Mole Ratios'. To the right, a man in a maroon shirt gestures while a black screen displays information about video resources.
A handwritten chemistry diagram showing the chemical reaction of nitrogen gas and hydrogen gas forming ammonia, with colored boxes highlighting the numbers 1, 2, and 3 in the reaction equation.