Overview
This lecture covers key formulas used in regular and solution stoichiometry, including calculations for moles, percent composition, yield, error, molarity, and dilution.
Moles and Molar Mass
- Moles (n) = mass (g) ÷ molar mass (g/mol)
- Mass (g) = moles × molar mass
- Molar mass (g/mol) = mass ÷ moles
- One mole equals Avogadro’s number: 6.02 × 10²³ particles
Percent Composition, Yield, and Error
- Percent composition = (mass of element ÷ total mass of compound) × 100%
- Percent yield = (actual yield ÷ theoretical yield) × 100%
- Percent error = [(measured value – actual value) ÷ actual value] × 100%
- Absolute error = |measured value – actual (true) value|
Solution Concentration (Molarity)
- Molarity (M) = moles of solute (n) ÷ volume of solution (L)
- Moles = molarity × volume
- Volume = moles ÷ molarity
- Solute: substance dissolved (e.g., NaCl); solvent: does the dissolving (e.g., water); solution: solute + solvent mixture
Dilution Formula
- Dilution equation: M₁V₁ = M₂V₂
- Used to find new concentration after adding solvent (e.g., water)
- The number of moles of solute remains constant during dilution (M₁V₁ = M₂V₂ because both equal n)
Key Terms & Definitions
- Mole — A quantity representing 6.02 × 10²³ entities (Avogadro's number)
- Molar mass — Mass of one mole of a substance (g/mol)
- Solute — Substance being dissolved in a solution
- Solvent — Substance that dissolves the solute
- Solution — Homogeneous mixture of solute and solvent
- Molarity — Concentration of a solution, moles of solute per liter of solution
Action Items / Next Steps
- Review example problems using these formulas
- Download the provided formula sheet for reference