NCERT Questions

Class 9
Chapter 2 Class 9 - Is Matter Around Us Pure

## solubility of a salt?

(a) At 313K,

Mass of potassium nitrate needed to produce a saturated solution of potassium nitrate in 100g water = 62g

Mass of potassium nitrate needed to produce a saturated solution of potassium nitrate in 1g water = 62g/100g

Mass of potassium nitrate needed to produce a saturated solution of potassium nitrate in 1g water = 62gx50g/100g

= 62g/2

=31 g

(b) Solubility of solids in liquid decreases with decrease in temperature.

Room temperature is 298K while the saturated solution was formed at 253K. Hence, she will find crystals of potassium chloride when the solution cools down.

(c) Solubility is the maximum amount of solute which can be dissolved in 100 gm of Solvent at a particular temperature.

Hence the solubility of the following at 293K is

• Potassium Nitrate - 32
• Sodium Chloride - 36
• Potassium Chloride - 35
• Ammonium Chloride - 37

(d) From the above table we can see that the solubility of a salt is directly proportional to the temperature.

As the temperature increases the solubility also increases.

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