Select the correct statement about osmolarity.

• A. Osmolarity is always equal to the molarity of the solution.
• B. Osmolarity measures only the concentration of ionic solutes in a solution.
• C. Osmolarity is defined as the total concentration of solute particles per liter of solution.
• D. Osmolarity is expressed in units of mol/kg.

Answer: (C)

Verified step by step guidance

1. Understand that osmolarity is a measure of the total concentration of all solute particles in a solution, regardless of whether they are ionic or molecular.
2. Recall that osmolarity is expressed as the number of osmoles of solute particles per liter of solution, which means its units are osmoles per liter (Osm/L), not mol/kg.
3. Recognize that osmolarity differs from molarity because molarity counts moles of solute formula units, while osmolarity counts all particles resulting from dissociation or association in solution.
4. Note that osmolarity includes contributions from both ionic and non-ionic solutes, so it is not limited to ionic solutes only.
5. Conclude that the correct statement is: 'Osmolarity is defined as the total concentration of solute particles per liter of solution.'