Question

Explain the difference between molarity and molality of a solution. How does a change in temperature influence their values?

Hint:

Molarity changes with temperature due to volume expansion, whereas molality remains constant as it depends only on mass.

Answer 1

Step 1: Definition - Molarity (M): Number of moles of solute per liter of solution. \[ M = \frac{\text{moles of solute}}{\text{volume of solution in liters}} \] - Molality (m): Number of moles of solute per kg of solvent. \[ m = \frac{\text{moles of solute}}{\text{mass of solvent in kg}} \] Step 2: Effect of Temperature - Molarity depends on volume, which changes with temperature due to thermal expansion. Thus, molarity decreases with an increase in temperature. - Molality depends on the mass of the solvent, which remains unaffected by temperature, making it temperature-independent.