Which statement is false about molarity and molality?

• A. Molarity uses kilograms of solvent; Molality uses liters of solution.
• B. Molality uses liters of solution; Molarity uses kilograms of solvent.
• C. Molality uses kilograms of solvent; Molarity uses liters of solution.
• D. Both are independent of temperature.

Answer: (C)

Understanding molarity and molality comes down to how each concentration is defined. Molarity is moles of solute per liter of solution, so it depends on the volume of the solution. Molality is moles of solute per kilogram of solvent, so it depends on the mass of the solvent. This statement matches those definitions: molality uses kilograms of solvent, and molarity uses liters of solution. Because volume changes with temperature, molarity can shift as the solution expands or contracts, while molality, based on solvent mass, remains essentially unchanged with temperature. This distinction is why the two measures behave differently in temperature-dependent contexts and why choosing the mass-based versus volume-based description is crucial. The other ideas blur the roles of mass and volume or assume temperature independence for both, which isn’t accurate in practice.