Question

Concentration terms like mass percentage, ppm, mole fraction and molality do not depend on temperature. However, molarity is a function of temperature because

• A. volume depends on temperature and molarity involves volume
• B. molarity involves non-volatile solute while all other terms involve volatile solute
• C. number of moles of solute change with change in temperature
• D. molarity is used for polar solvents only

Answer 1

Answer: (A)

Molarity $=\frac{\text{ no. of moles }}{\text{ Volume of solution }(L)}$
When temperature increases the volume of the solution decreases assuming the solution is in constant pressure conditions.
$T\alpha \frac{1}{V}$
Therefore when temperature increases volume decreases and molarity increases.
Mass percentage, ppm, mole fraction and molality are solely dependant on mass which is independent of temperature.