Mole Ratio Calculator

Calculate mole conversions and stoichiometric ratios from balanced chemical equations

From (Given Substance)

To (Desired Substance)

Understanding Mole Ratios

Mole ratios are the heart of stoichiometry. They represent the relationship between the amounts of reactants and products in a chemical reaction, as shown by the coefficients in a balanced chemical equation. These ratios allow us to predict how much product will form or how much reactant is needed for a complete reaction.

Key Concepts

  • Stoichiometric Coefficient: The number before each substance in a balanced equation (e.g., the "2" in 2Hâ‚‚)
  • Mole Ratio: The ratio of moles between two substances, derived from their coefficients
  • Balanced Equation: A chemical equation where atoms are conserved (same number on both sides)
  • Conversion Factor: A multiplier used to convert moles of one substance to moles of another
  • Law of Conservation of Mass: Matter cannot be created or destroyed in chemical reactions

How to Use This Calculator

Step 1: Select or Enter Your Reaction

Choose a predefined reaction from the dropdown menu, or select "Custom Reaction" to work with your own balanced equation.

Step 2: Set Up the Conversion

In the blue box (From), enter:

  • The substance you're starting with
  • Its coefficient from the balanced equation
  • How many moles you have

Step 3: Specify What You Want to Find

In the green box (To), enter:

  • The substance you want to calculate
  • Its coefficient from the balanced equation

Step 4: Calculate

Click "Calculate Mole Ratio" to see the mole ratio, the calculated number of moles, and a step-by-step explanation of the conversion.

Example Problems

Example 1: Water Formation

Reaction: 2H₂ + O₂ → 2H₂O

Question: If you have 4.0 moles of Hâ‚‚, how many moles of Hâ‚‚O can you produce?

Solution:

Mole ratio: Hâ‚‚ : Hâ‚‚O = 2 : 2 = 1 : 1
Calculation: 4.0 mol H₂ × (2 mol H₂O / 2 mol H₂) = 4.0 mol H₂O
Answer: 4.0 moles of Hâ‚‚O

Example 2: Ammonia Synthesis

Reaction: N₂ + 3H₂ → 2NH₃

Question: How many moles of H₂ are needed to produce 6.0 moles of NH₃?

Solution:

Mole ratio: NH₃ : H₂ = 2 : 3
Calculation: 6.0 mol NH₃ × (3 mol H₂ / 2 mol NH₃) = 9.0 mol H₂
Answer: 9.0 moles of Hâ‚‚

Example 3: Methane Combustion

Reaction: CH₄ + 2O₂ → CO₂ + 2H₂O

Question: If 2.5 moles of Oâ‚‚ are consumed, how many moles of COâ‚‚ are produced?

Solution:

Mole ratio: Oâ‚‚ : COâ‚‚ = 2 : 1
Calculation: 2.5 mol O₂ × (1 mol CO₂ / 2 mol O₂) = 1.25 mol CO₂
Answer: 1.25 moles of COâ‚‚

Common Chemical Reactions and Ratios

Synthesis Reactions

2H₂ + O₂ → 2H₂O

Ratios: Hâ‚‚:Oâ‚‚ = 2:1, Hâ‚‚:Hâ‚‚O = 2:2 = 1:1, Oâ‚‚:Hâ‚‚O = 1:2

N₂ + 3H₂ → 2NH₃

Ratios: N₂:H₂ = 1:3, N₂:NH₃ = 1:2, H₂:NH₃ = 3:2

Combustion Reactions

CH₄ + 2O₂ → CO₂ + 2H₂O

Ratios: CHâ‚„:Oâ‚‚ = 1:2, CHâ‚„:COâ‚‚ = 1:1, Oâ‚‚:Hâ‚‚O = 2:2 = 1:1

C₃H₈ + 5O₂ → 3CO₂ + 4H₂O

Ratios: C₃H₈:O₂ = 1:5, C₃H₈:CO₂ = 1:3, O₂:CO₂ = 5:3

Decomposition Reactions

2H₂O → 2H₂ + O₂

Ratios: Hâ‚‚O:Hâ‚‚ = 2:2 = 1:1, Hâ‚‚O:Oâ‚‚ = 2:1, Hâ‚‚:Oâ‚‚ = 2:1

2KClO₃ → 2KCl + 3O₂

Ratios: KClO₃:KCl = 2:2 = 1:1, KClO₃:O₂ = 2:3

Neutralization Reactions

HCl + NaOH → NaCl + H₂O

Ratios: All 1:1:1:1

2HCl + Ca(OH)₂ → CaCl₂ + 2H₂O

Ratios: HCl:Ca(OH)â‚‚ = 2:1, HCl:Hâ‚‚O = 2:2 = 1:1

Tips for Working with Mole Ratios

  • Always balance your equation first - Mole ratios only work with balanced equations
  • Write out the ratio - Clearly identify which coefficients correspond to your substances
  • Use dimensional analysis - Set up your calculation so units cancel properly
  • Simplify ratios when possible - 2:4 is the same as 1:2 and easier to work with
  • Check your work - Make sure your answer makes chemical sense
  • Keep track of significant figures - Your answer should match the precision of your given data
  • Remember: mole ratios are exact - Unlike measurements, stoichiometric coefficients don't limit significant figures
  • Practice with different types of reactions - Each type has its own patterns

Mole Ratios in Context

Mole ratios are just one piece of stoichiometry calculations. Here's how they fit into the bigger picture:

Complete Stoichiometry Workflow

1.
Mass to Moles: Convert given mass to moles using molar mass
moles = mass (g) ÷ molar mass (g/mol)
2.
Mole Ratio: Convert moles of one substance to moles of another
Use coefficients from balanced equation
3.
Moles to Mass: Convert moles back to mass if needed
mass (g) = moles × molar mass (g/mol)

Remember: Mole ratios ONLY convert between moles. To work with grams, you must first convert to moles, then use the mole ratio, then convert back to grams if needed.

References

The calculations and concepts used in this calculator are based on fundamental stoichiometry principles from reputable sources:

Note: This calculator assumes you're working with balanced chemical equations. The mole ratios derived from stoichiometric coefficients are exact values based on the law of conservation of mass. Always ensure your equation is properly balanced before using mole ratio calculations.

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