Solubility
The maximum amount of a solute which can be dissolved in 100 grams of a solvent at a specified temperature is known as the solubility of that solute in that solvent (at that temperature). If the solvent is water, then we can define solubility as follows : The maximum amount of a solute which can be dissolved in 100 grams of water at a given temperature, is the solubility of that solute in water (at that temperature).Please note that solubility is always stated as 'mass of solute per 100 gram of water' (or any other solvent).For example: (a) A maximum of 32 grams of potassium nitrate can be dissolved in 100 grams of water at 20°C,therefore, the solubility of potassium nitrate in water is 32 grams at 20°C. (b) A maximum of 36 grams of sodium chloride (common salt) can be dissolved in 100 grams of water at 20°C, therefore, the solubility of sodium chloride (or common salt) in water is 36 grams at 20°C. (b) A maximum of 36 grams of sodium chloride (common salt) can be dissolved in 100 grams of water at 20°C, therefore, the solubility of sodium chloride (or common salt) in water is 36 grams at 20°C. From the above discussion it is obvious that the solubility of a substance (or solute) refers to its saturated solution. So, we can write a yet another definition of solubility as follows :The solubility of a solute in water at a given temperature is the number of grams of that solute which can be dissolved in 100 grams of water to make a saturated solution at that temperature. The solubility of different substances in water is different. Since the solubility depends on temperature, so while expressing the solubility of a substance, we have to specify the temperature also.The solubilities of some of the substances (or solutes) are given below. All these values of solubilities are 'per 100 grams of water'.
Substance
(or Solute) | Solubility in water
(at 20°C) |
1.Copper sulphate
2.Potassium nitrate
3.Potassium chloride
4.Sodium chloride
5.Ammonium chloride
6.Sugar | 21 g
32 g
34 g
36 g
37 g
204 g |
Sample Problem. 12 grams of potassium sulphate dissolves in 75 grams of water at 60°C. What is its solubility in water at that temperature ? Solution. Here we have been given that 75 grams of water dissolves 12 grams of potassium suphate.We have to find how much potassium sulphate will dissolve in 100 grams of water. Now 75 g of water dissolves = 12 g of potassium sulphate So,100 g of water will dissolve = 1275x100 g of potassium sulphate
= 16 gram of potassium sulphate
Thus, the solubility of potassium sulphate in water is 16 g at 60°C.
Notes
Matter in Our Surroundings - Notes
1. 11. Metals Usually Have a Silver or Grey Colour
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2. The Case of a Liquid Solute Dissolved in a Liquid Solvent
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8. 7. Non-Metals may be Solid, Liquid or Gases at the Room Temperature.
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10. 3. Non-Metals are Bad Conductors of Heat and Electricity.
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11. 6. Metals are Usually Strong. They Have High Tensile Strength.
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17. Chemical Formula for daily use material
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24. To Study the Properties of a Compound of Iron and Sulphur
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28. 4. Metals are Lustrous (or Shiny), and can be Polished.
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30. To Separate a Mixture of Alcohol and Water
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31. To Study the Properties of a Solution
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35. 7. Metals are Solids at the Room Temperature
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36. To Study the Properties of a Suspension
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39. To Separate the Salt-Water Mixture (or Salt-Solution)
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46. Separation of Mixture Of Two Solids
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49. 6. Non-Metals are Not Strong. They Have Low Tensile Strength.
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