Chemistry
Solutions and Concentration
Solution
A solution is a homogeneous system consisting of two or more components.
| Quantity | Formula |
|---|---|
| ω (percent) | m(substance) / m(solution) · 100 |
| CM (mol/l) | n / V |
| Dilution | m₁ω₁ = m₂ω₂ |
| Saturated ω | S / (100 + S) · 100 |
CM is the molar concentration. n is the amount of substance, V is the volume (l).
Key facts
- m(solution) = m(substance) + m(solvent). Also m(solution) = ρ · V.
- Volume (l) is found by dividing the volume in ml by 1000.
- CM = 10ρω / M (ρ in g/ml, ω in percent).
- Solubility: S: the saturated amount per 100 g of solvent. That is, the mass of substance dissolved in 100 g of solvent in a saturated solution at a given temperature.
- There are unsaturated, saturated and supersaturated solutions.
- As temperature increases, the solubility of solids often increases, while that of gases decreases.
Dilution and mixing
- During dilution, m(substance) does not change.
- Mass of added water: m(H₂O) = m₂ − m₁.
- When mixing solutions, the "cross rule" is used.
- Crystalline hydrates contain water of crystallization: CuSO₄·5H₂O.
Example: 200 g of a 15% solution contains 30 g of salt.