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प्रश्न
Pragya tested the solubility of three different substances at different temperatures and collected the data as given below (results are given in the following table, as grams of substance dissolved in 100 grams of water to form a saturated solution).
| Substance dissolved | Temperature in K | ||||
| 283 | 293 | 313 | 333 | 353 | |
| Solubility | |||||
| Potassium nitrate | 21 | 32 | 62 | 106 | 167 |
| Sodium chloride | 36 | 36 | 36 | 37 | 37 |
| Potassium chloride | 35 | 35 | 40 | 46 | 54 |
| Ammonium chloride | 24 | 37 | 41 | 55 | 66 |
- What mass of potassium nitrate would be needed to produce a saturated solution of potassium nitrate in 50 grams of water at 313 K?
- Pragya makes a saturated solution of potassium chloride in water at 353 K and leaves the solution to cool at room temperature. What would she observe as the solution cools? Explain.
- Find the solubility of each salt at 293 K. What salt has the highest solubility at this temperature?
- What is the effect of change of temperature on the solubility of a salt?
उत्तर
a) Solubility of potassium nitrate at 313 K `62/100`
100 g of water contains potassium nitrate = 62g
50 g of water contains potassium nitrate = `62/100 xx 50` = 31 g
Thus, 31 g of potassium nitrate would be needed to produce a saturated solution of potassium nitrate in 50 g of water at 313K
b) At 313 K, dissolve magnesium nitrate in 50 g of water. (a) As a saturated solution of potassium chloride at 353 K is cooled, its solubility in water drops. As a result, crystals form when the amount of potassium chloride exceeds its solubility at lower temperatures.
c) Solubility refers to the quantity of salt that may dissolve in 100 g of water to create a saturated solution at a specific temperature.
Solubility of potassium nitrate at 293 K = `32/100`
Solubility of sodium chloride at 293 K = `36/100`
Solubility of potassium chloride at 293 K = `35/100`
Solubility of ammonium chloride at 293 K = `37/100`
From the above data, it is clear that ammonium chloride has the highest solubility at 293 K.
d) In general, a salt's solubility increases with temperature. However, the rise varies depending on the salt. For example, the solubility of potassium nitrate increases significantly, that of ammonium chloride increases somewhat, that of potassium chloride increases marginally, and that of sodium chloride remains nearly unchanged.
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