Calculate mole ratios and quantities in chemical reactions based on balanced equations
The stoichiometry calculator uses balanced chemical equations to determine quantitative relationships between reactants and products. It calculates mole ratios, converts between mass and moles, identifies limiting reagents, and predicts product amounts based on the law of conservation of mass and definite proportions.
n = m / M
moles = mass (g) / molar mass (g/mol)
Mole-Mass Relationship
n = m/M where n = moles, m = mass, M = molar mass
Mole Ratio
Use coefficients from balanced equation: aA + bB → cC + dD
Product Calculation
moles_product = moles_reactant × (coefficient_product / coefficient_reactant)
Mass of Product
mass_product = moles_product × molar_mass_product
Example Reaction:
2H₂ + O₂ → 2H₂O
If 4 g H₂ reacts: 4 g ÷ 2 g/mol = 2 mol H₂ → produces 2 mol H₂O = 36 g H₂O
Write Balanced Equation
N₂ + 3H₂ → 2NH₃
Given: 28 g N₂. How much NH₃ forms?
Convert Mass to Moles
Molar mass N₂ = 28 g/mol
moles N₂ = 28 g / 28 g/mol = 1.0 mol
Apply Mole Ratio
From equation: 1 mol N₂ produces 2 mol NH₃
moles NH₃ = 1.0 mol N₂ × (2 mol NH₃ / 1 mol N₂) = 2.0 mol NH₃
Convert Moles to Mass
Molar mass NH₃ = 17 g/mol
mass NH₃ = 2.0 mol × 17 g/mol = 34 g NH₃
Unbalanced equations
Always verify the equation is balanced before calculations
Skipping mole conversions
Must convert between mass and moles using molar mass
Wrong mole ratios
Use coefficients from balanced equation, not subscripts
Incorrect molar mass
Calculate molar mass carefully from periodic table
Identify the limiting reactant
Calculate reaction efficiency
Calculate maximum product formation
Stoichiometry is the branch of chemistry that deals with the quantitative relationships between reactants and products in chemical reactions. It's based on the law of conservation of mass and allows us to predict how much product forms from given reactants.
Moles represent the number of particles (atoms, molecules) and are directly related to the coefficients in balanced equations. Chemical reactions occur by particle collisions, not by mass, so we must work in moles to apply mole ratios correctly.
Add up the atomic masses of all atoms in the formula. For H₂O: (2 × 1.008) + 16.00 = 18.016 g/mol. Use the periodic table for atomic masses and multiply by the subscript for each element.
Coefficients (numbers before formulas like 2H₂O) indicate the number of molecules/moles and are used in stoichiometry calculations. Subscripts (numbers within formulas like H₂O) show the number of atoms within one molecule and are used to calculate molar mass.
No, the equation must be balanced first. Unbalanced equations don't conserve mass and give incorrect mole ratios. Always balance your equation before performing any stoichiometric calculations.
You need to identify the limiting reagent first - the reactant that produces the least amount of product. Use that reactant's amount to calculate product formation, as it will be consumed first and stop the reaction.
Stoichiometry gives theoretical yields assuming 100% reaction completion and perfect conditions. Real reactions have lower percent yields due to side reactions, incomplete reactions, or losses during product recovery.
Stoichiometry is essential in pharmaceutical manufacturing (drug synthesis), industrial chemistry (fertilizers, plastics), environmental science (pollution control), food chemistry (baking ratios), and any field requiring precise chemical quantities.
Education
Core chemistry curriculum and problem-solving
Laboratory
Precise reagent preparation and analysis
Industry
Chemical manufacturing and process optimization
Research
Synthesis planning and yield prediction