Question

Which of the following is dependent on temperature?

• A. Molarity
• B. Mole fraction
• C. Weight percentage
• D. Molality

Answer 1

The Correct Option is A

To determine which of the given options is dependent on temperature, let's first define and analyze each term:

1. Molarity: Molarity is defined as the number of moles of solute per liter of solution. Its formula is: M = \frac{\text{moles of solute}}{\text{volume of solution in liters}}. Since volume is affected by temperature (as most liquids expand or contract with changes in temperature), molarity is temperature-dependent.
2. Mole Fraction: The mole fraction of a component in a mixture is the ratio of the number of moles of that component to the total number of moles of all components in the mixture. The formula is: x_i = \frac{\text{moles of component } i}{\text{total moles of all components}}. Mole fraction is dimensionless and purely depends on the number of moles, not on volume, so it is not temperature-dependent.
3. Weight Percentage: This is the mass of solute divided by the total mass of the solution, multiplied by 100: \text{Weight Percentage} = \frac{\text{mass of solute}}{\text{mass of solution}} \times 100. Since this is a mass-based measure, it is independent of temperature changes.
4. Molality: Molality is defined as the number of moles of solute per kilogram of solvent. Its formula is: m = \frac{\text{moles of solute}}{\text{mass of solvent in kg}}. Since molality is based on mass, which does not change with temperature, it is also temperature-independent.

Therefore, the correct answer is Molarity, as it is indeed the only concentration measure from the list that depends on temperature due to its dependence on the volume of the solution.

Conclusion: Molarity changes with temperature because the volume of liquid components changes with temperature, making it temperature-dependent.