Question

Choose the correct answer :
When temperature of a solution increases then –
(a) Molarity decreases and molality increases
(b) Molality decreases and molarity increases
(c) No change occur for both molarity and molality
(d) Molarity increases and no change in molality.​

Answer 1

Answer: option d

Molarity decreases no change in molality

Explanation:

Molality is independent of temperature.

Answer 2

When temperature of any given solution is increased, the molarity of the solution decreases while the molality of the solution remains constant.

• Molarity is defined as the number of mole of solute present per unit volume(litre) of the solution.
• Molality is defined as the number of moles of solute present per unit mass(kg) of the solvent.
• The increase in temperature leads to an expansion in the volume of the solution but the mass remains constant.
• Since, molarity is inversely proportional to the volume of the solution, an expansion in the volume leads to decrease in the molarity.
• As, the mass is constant, there is no effect of change of temperature on the molality of the solution.