Solutions - Formula Sheet
Core Equations and Ratios of Solutions
The following are the essential mathematical formulas, mass-volume relations, and concentration equations used in the Solutions chapter:
1. Solubility of a Solute
\[\text{Solubility (g/100 g solvent)} = \frac{\text{Mass of solute (g)}}{\text{Mass of solvent (g)}} \times 100\]
- Mass of solute: The mass in grams of the solute substance dissolved in the solvent.
- Mass of solvent: The mass in grams of the pure solvent medium (typically water, which has a mass of 1 g per 1 mL).
2. Concentration by Mass Percentage (w/w)
\[\text{Mass Percentage (\% w/w)} = \frac{\text{Mass of solute (g)}}{\text{Mass of solution (g)}} \times 100\]
\[\text{Mass Percentage (\% w/w)} = \frac{\text{Mass of solute (g)}}{\text{Mass of solute (g)} + \text{Mass of solvent (g)}} \times 100\]
- Mass of solution: The combined mass of both the dissolved solute and the solvent.
3. Concentration by Volume Percentage (v/v)
\[\text{Volume Percentage (\% v/v)} = \frac{\text{Volume of solute (mL)}}{\text{Volume of solution (mL)}} \times 100\]
\[\text{Volume Percentage (\% v/v)} = \frac{\text{Volume of solute (mL)}}{\text{Volume of solute (mL)} + \text{Volume of solvent (mL)}} \times 100\]
- Volume of solute: The volume in milliliters of the liquid solute.
- Volume of solvent: The volume in milliliters of the liquid solvent.
- Volume of solution: The combined volume of the liquid solute and solvent, which can be temperature-dependent.
4. Water of Crystallization in Hydrated Salts
Hydrated salts are represented by chemical formulas indicating the ratio of water molecules bound to the ionic salt unit:
- Copper(II) sulphate pentahydrate (Blue Vitriol): \[CuSO_4 \cdot 5H_2O\] (5 molecules of crystallization water per formula unit)
- Magnesium sulphate heptahydrate (Epsom Salt): \[MgSO_4 \cdot 7H_2O\] (7 molecules of crystallization water per formula unit)
- Calcium sulphate dihydrate (Gypsum): \[CaSO_4 \cdot 2H_2O\] (2 molecules of crystallization water per formula unit)
- Iron(II) sulphate heptahydrate (Green Vitriol): \[FeSO_4 \cdot 7H_2O\] (7 molecules of crystallization water per formula unit)
- Zinc sulphate heptahydrate (White Vitriol): \[ZnSO_4 \cdot 7H_2O\] (7 molecules of crystallization water per formula unit)