Molality is defined as what?

Molality is defined as what?

• A. m = moles solute / kg solvent
• B. m = moles solute / L solution
• C. m = moles solvent / kg solute
• D. m = grams solute / kg solvent

Answer: (A)

Molality is defined as the amount of solute in moles divided by the mass of solvent in kilograms. This way of expressing concentration depends on the number of particles relative to the mass of the solvent, not the solution’s volume, which helps keep it relatively stable with temperature changes. So the proper formula is moles of solute per kilogram of solvent. Using per liter of solution would be molarity, using kilograms of solute would invert the ratio, and using grams instead of moles changes the unit entirely.

Molality is defined as the amount of solute in moles divided by the mass of solvent in kilograms. This way of expressing concentration depends on the number of particles relative to the mass of the solvent, not the solution’s volume, which helps keep it relatively stable with temperature changes. So the proper formula is moles of solute per kilogram of solvent. Using per liter of solution would be molarity, using kilograms of solute would invert the ratio, and using grams instead of moles changes the unit entirely.