Molality is independent of temperature. Which statement is true?

• A. Molality is independent of temperature.
• B. Molality depends on volume.
• C. Molality is defined per liter of solution.
• D. Molality increases with temperature.

Answer: (A)

Molality is defined as the amount of solute per kilogram of solvent, so it depends on mass, not volume. Since mass is conserved and does not change with temperature (aside from negligible evaporation), molality stays essentially constant as temperature changes. This is why it’s considered independent of temperature.

In contrast, molarity uses volume in its denominator (moles per liter of solution), and volume changes with temperature due to thermal expansion. That’s why molarity can vary with temperature, even though the amount of solute and solvent may not. The statement that molality is defined per liter of solution describes molarity, not molality, and the idea that molality increases with temperature isn’t correct because molality doesn’t rely on volume or temperature in the way molarity does.