Convert between grams, moles, and molecules/atoms. Find limiting reactants, calculate theoretical and percent yield using balanced chemical equations.
Convert: Grams ↔ Moles ↔ Molecules/Atoms/Formula Units
Determine which reactant runs out first and limits product formation
% Yield = (Actual / Theoretical) × 100
Calculate products from reactants using balanced equation
Stoichiometry is the calculation of reactants and products in chemical reactions. It uses balanced equations and molar relationships to predict amounts.
1) Grams to Moles
How many moles in 18 g of H₂O? (MM = 18.015 g/mol)
moles = 18 g / 18.015 g/mol = 0.999 mol ≈ 1 mol
2) Limiting Reactant
Reaction: 2H₂ + O₂ → 2H₂O
Given: 4 g H₂ (MM=2) and 32 g O₂ (MM=32)
Moles H₂: 4/2 = 2 mol → needs 1 mol O₂ (ratio 2:1)
Moles O₂: 32/32 = 1 mol → needs 2 mol H₂
Both exactly match → No limiting reactant!
If we had only 0.5 mol O₂, it would be limiting.
3) Percent Yield
Theoretical yield: 50 g, Actual yield: 45 g
% Yield = (45 / 50) × 100 = 90%
4) Gas at STP
At STP (0°C, 1 atm): 1 mole gas = 22.4 L
2 moles H₂ = 2 × 22.4 = 44.8 L
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