Question

Atul tested the solubility of four different substances at different temperatures and data are noted in the following table. (Results are given in grams/100 grams of water to form a saturated solution).

(a) What mass of potassium nitrate would be needed to prepare a saturated solution of potassium nitrate in 50 grams of water at 323 K?​

(b) The saturated solution of potassium chloride at 363K is cooled to room temperature. What would Atul observe as the solution cools?​

Answer 1

(a) At 323 K, 100 g of water can dissolve a maximum of 82 g of potassium nitrate. ​
A saturated solution of 1 g of water requires 82/100 g potassium nitrate. [0.5 Mark]​
To produce a saturated solution of potassium nitrate in 50 g of water at 323 K, ​

We need (82 $\times$ 50)/100 = 41 g of potassium nitrate [0.5 Mark]​

​(b) When a saturated solution of potassium chloride is cooled at 363 K, the solubility of potassium chloride in water decreases. Due to this, the amount of potassium chloride which exceeds its solubility at lower temperature, separates out as crystals. [1 Mark]​