Effect of Temperature and Pressure on Solubility
The effect of temperature and pressure on the solubility of a substance is as follows : i) The solubility of solids in liquids usually increases on increasing the temperature; and decreases on decreasing the temperature. (ii) The solubility of solids in liquids remains unaffected by the changes in pressure. iii) The solubility of gases in liquids usually decreases on increasing the temperature; and increases on decreasing the temperature. (iv) The solubility of gases in liquids increases on increasing the pressure; and decreases on decreasing the pressure. We will describe the effect of temperature on the solubility of a solid substance in water in a little more detail. Look at the solubilities of copper sulphate in water at various temperatures given below :
| Temperature | Solubility of copper sulphate |
0°C
10°C
20°C
30°C
40°C
50°C
60°C
70°C | 14 g
17 g
21 g
24 g
29 g
34 g
40 g
47 g |
We can see from this data that as the temperature is increased from 0°C to 70°C the solubility of copper sulphate in water increases from 14 grams to 47 grams. Now, let us see what happens when we cool a saturated solution of copper sulphate from a higher temperature to a lower temperature. The solubility of copper sulphate at 70°C is 47 grams and the solubility of copper sulphate at 20°C is 21 grams (as shown in the above table). This means that 100 grams of water can dissolve a maximum of 47 grams of copper sulphate at 70°C but only 21 grams at 20°C. So, if we cool a saturated solution of copper sulphate made in 100 grams of water from 70°C to 20°C, then the solubility of copper sulphate will decrease and 47 grams - 21 grams = 26 grams of copper sulphate will separate out from the solution in the form of solid crystals. Let us solve a problem now.Sample Problem. A student determined the solubility of four substances, potassium nitrate sodium chloride, potassium chloride and ammonium chloride in water at five different temperatures of 10°C, 20°C,40°C 60°C 80°C and obtained the following data :
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Matter in Our Surroundings - Notes
2. 7. Metals are Solids at the Room Temperature
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4. 3. Non-Metals are Bad Conductors of Heat and Electricity.
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8. 11. Non-Metals Have Many Different Colours.
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9. 7. Non-Metals may be Solid, Liquid or Gases at the Room Temperature.
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16. 8. Metals Generally Have High Melting Points and Boiling Points.
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19. 8. Non-Metals Have Comparatively Low Melting Points and Boiling Points
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23. To Study the Properties of a Suspension
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24. Chemical Formula for daily use material
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25. 1. Non-Metals are Not Malleable. Non-Metals are Brittle.
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26. Effect of Temperature and Pressure on Solubility
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31. Pure Substances : Elements and Compounds
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32. 3. Metals are Good Conductors of Heat and Electricity.
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33. 4. Non-Metals are Not Lustrous (Not Shiny). They are Dull in Appearance.
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37. 1. Separation by a Suitable Solvent
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38. Solutions, Suspensions And Colloids
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46. Differences Between Mixtures and Compounds
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48. Separation Of Mixture Of a Solid And a Liquids
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50. To Separate the Salt-Water Mixture (or Salt-Solution)
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