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# 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 a substance dissolved in 100 grams of water to form a saturated solution). (a) What mass of potassium nitrate would be needed to produce a saturated solution of potassium nitrate in 50 grams of water at 313K? (b) 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. (c) Find the solubility of each salt at 293 K. Which salt has the highest solubility at this temperature? (d) What is the effect of change of temperature on the solubility of a salt?

(a) Given:

Mass of potassium nitrate required to produce a saturated solution in 100 g of water at 313 K = 62g

Mass of potassium nitrate required to produce a saturated solution in 50 g of water

#### = $$62$$ × $$50 \over 100$$ $$= 31 \ g$$

Hence 31 g of potassium nitrate is required to form a saturated solution of it at the given temperature.

(b) Pragya would observe crystals of potassium chloride as the solubility of potassium chloride in water decreases when a saturated solution of potassium chloride loses its heat during the cooling process below 353 K.

(c) Listed below is the solubility of each salt at 293 K:

Solubility of Potassium nitrate —> 32g

Solubility of Sodium chloride —> 36g

Solubility of Potassium chloride —> 35g

Solubility of Ammonium chloride —> 37g

Ammonium chloride has the highest solubility at this temperature.

(d) Solubility of a salt is directly proportional to the change of temperature. Solubility of salt will increase when the temperature increases and solubility will decrease when the temperature decreases .