Solubility is calculated by determining the mass of solute that dissolves in a given mass of solvent, typically expressed as grams of solute per 100 grams of solvent (g/100g). Here's a breakdown of the process:
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Determine the Mass of Solute Dissolved: Measure the mass (in grams) of the solute that has completely dissolved in the solution. This is often obtained through experimental observation.
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Determine the Mass of Solvent: Measure the mass (in grams) of the solvent used in the solution.
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Calculate the Solubility Ratio: Divide the mass of the solute by the mass of the solvent.
Solubility Ratio = Mass of Solute (g) / Mass of Solvent (g) -
Express as Grams per 100 Grams of Solvent: Multiply the solubility ratio by 100 to express the solubility in grams of solute per 100 grams of solvent (g/100g).
Solubility (g/100g) = (Mass of Solute (g) / Mass of Solvent (g)) * 100
Example:
Suppose you dissolve 20 grams of sugar in 80 grams of water. To calculate the solubility:
- Mass of solute (sugar) = 20 g
- Mass of solvent (water) = 80 g
- Solubility Ratio = 20 g / 80 g = 0.25
- Solubility (g/100g) = 0.25 * 100 = 25 g/100g
Therefore, the solubility of sugar in water in this specific scenario is 25 grams per 100 grams of water.
Important Considerations:
- Temperature Dependence: Solubility is heavily influenced by temperature. Always specify the temperature at which the solubility is measured.
- Units: While g/100g is common, other units like molarity (mol/L) or parts per million (ppm) may be used depending on the context.
- Saturation: This calculation provides the solubility at saturation. A solution can be unsaturated (less solute dissolved than the solubility limit) or supersaturated (more solute dissolved than the solubility limit, usually unstable).
In summary, calculating solubility involves determining the ratio of solute to solvent in a saturated solution and expressing it in a standard unit like grams per 100 grams of solvent, considering factors like temperature for accurate representation.
