Stoichiometry Calculator – Balance Chemical Reactions Instantly
Solve stoichiometry problems effortlessly with our stoichiometry calculator. Input your balanced chemical equation coefficients and known quantities to find moles, grams, or molecules of reactants and products. A must-have tool for chemistry students.
Stoichiometry calculates the quantities of reactants and products in chemical reactions. You use balanced chemical equations to determine mole ratios between substances. These ratios let you convert between amounts of different reactants and products.
Stoichiometry Steps
- Write and balance the chemical equation
- Convert given quantities to moles
- Use mole ratios from coefficients to find moles of unknown
- Convert moles of unknown to desired units
Example: Combustion of Methane
From this equation:
- 1 mole CH₄ reacts with 2 moles O₂
- 1 mole CH₄ produces 1 mole CO₂ and 2 moles H₂O
- Mole ratio CH₄:O₂:CO₂:H₂O = 1:2:1:2
Stoichiometry Example Problem
How many grams of CO₂ form from 16 g of CH₄?
- Convert 16 g CH₄ to moles: 16 g / 16.04 g/mol = 1.0 mol CH₄
- Use mole ratio: 1 mol CH₄ produces 1 mol CO₂
- Convert to grams: 1.0 mol × 44.01 g/mol = 44.01 g CO₂
Enter values and calculate to see the graph
| Reaction | Reactant Ratio | Product Ratio |
|---|---|---|
| 2H₂ + O₂ → 2H₂O | 2:1 (H₂:O₂) | 2 (H₂O) |
| N₂ + 3H₂ → 2NH₃ | 1:3 (N₂:H₂) | 2 (NH₃) |
| 2KClO₃ → 2KCl + 3O₂ | 2 (KClO₃) | 2:3 (KCl:O₂) |
| C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O | 1:6 | 6:6 (CO₂:H₂O) |
- Determining reactant amounts in industrial synthesis
- Calculating theoretical and percent yield
- Identifying limiting reactants in reactions
- Scaling up laboratory reactions to production
- Environmental pollution calculations
What is stoichiometry used for?
Stoichiometry calculates the exact amounts of reactants needed and products formed in chemical reactions. Chemists use it to determine how much of each chemical to mix, predict reaction yields, and scale up from lab experiments to industrial production.
Why must chemical equations be balanced?
Balanced equations obey the law of conservation of mass—atoms aren't created or destroyed. The coefficients give you the mole ratios needed for stoichiometric calculations. An unbalanced equation gives wrong ratios and incorrect results.
What is a mole ratio?
A mole ratio is the ratio of coefficients between any two substances in a balanced equation. In 2H₂ + O₂ → 2H₂O, the H₂:O₂ ratio is 2:1, meaning 2 moles of hydrogen react with 1 mole of oxygen. Use these ratios to convert between substances.
How do you find the limiting reactant?
Calculate how much product each reactant could produce if fully consumed. The reactant that produces the least product is limiting—it runs out first and determines the maximum yield. Any excess reactant remains after the reaction stops.
What is the difference between theoretical and actual yield?
Theoretical yield is the maximum amount calculated from stoichiometry assuming perfect conditions. Actual yield is what you really get in the lab—always less due to incomplete reactions, side reactions, and losses during purification. Percent yield = (actual/theoretical) × 100%.
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