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Typically, the amount of solute that can be dissolved in a given amount of solvent at a given temperature is limited. When this limit is reached, we have a saturated solution, and any additional solute simply settles to the bottom of the solution.
A saturated solution is one in which no more solute can be dissolved in a specific amount of solvent at a given temperature.
Its solubility better explains the extent of a solute's dissolution in a solvent. Solubility measures how much of a solute can be dissolved in a given amount of a solvent.
Solubility is defined as the number of grams of a solute that can be dissolved in 100 g of a solvent to form its saturated solution at a given temperature and pressure.
Example:
To form a saturated solution at 25°C, 36 g of sodium chloride must be dissolved in 100 g of water. Thus, at 25°C, the solubility of NaCl in water is 36 g.
\text{Solubility} = \frac{\text{Mass of the solute}} {\text{Mass of the solvent}} \times 100
Let us see some of the solubility range of common substances in water at 25°C:
Name of the solute | Formula of the solute | Solubility g/100g water |
Calcium carbonate | CaCO_3 (s) | 0.0013 |
Sodium chloride | NaCl (s) | 36 |
Ammonia | NH_3 (g) | 48 |
Sodium hydroxide | NaOH(s) | 80 |
Glucose | C_6H_12O_6(s) | 91 |
Sodium bromide | NaBr(s) | 95 |
Sodium iodide | NaI(s) | 184 |
Recall: Solubility refers to the maximum amount of a substance dissolved in a given volume of solvent. Solubility in water is frequently expressed in gram/100mL.
An unsaturated solution is one that has not reached its maximum solubility. This means that more solute could be added to the solvent, and dissolving would continue.
A solution that has attained maximum solubility is called a saturated solution.
Supersaturated solutions are those in which the dissolved solute has risen above the normal saturation point. Typically, a condition such as increased temperature or pressure is required to produce a supersaturated solution.
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