Question

The solubility of potassium chloride (KCl) and Hydrogen chloride (HCl) for different temperatures is given in the table below:

Temperature (degree celsius)	10	20	30	40	50
Solubility (g per 100 ml), KCl	31.2	34.2	37.2	40.1	42.6
Solubility ( g per 100 ml), HCl	75	70	65.5	61	57.5

Let us assume you are asked to dissolve 75 g of HCl completely in a beaker containing 100 mL of water at ${40}^{\circ }C$. What should be done?

• A. Heat the solution to ${70}^{\circ }C$
• B. Cool the solution to ${10}^{\circ }C$
• C. Add 100 mL of water to it
• D. Add 1000 mL of water to it

Answer 1

Answer: (B), (C), (D)

The correct options are
B

Cool the solution to ${10}^{\circ }C$

C

Add 100 mL of water to it

D

Add 1000 mL of water to it

From the table, at ${40}^{\circ }C$, the solubility of HCl = 61 g/mL. At the given temperature, a maximum of 61 g of HCl can be dissolved in 100 mL of water.

At ${10}^{\circ }C$ the solubility of HCl increases to 75 g/mL. So, by decreasing the temperature to ${10}^{\circ }C$, HCl can be completely dissolved.

Also, by adding more solvent, i.e., water in this case, more solute can be made to dissolve.