How is osmolarity defined?

Osmolarity is defined as the concentration of solutes in a solution and is typically expressed in terms of osmoles of solute per liter of solution. This definition applies to all solutes present in the solution, including electrolytes and non-electrolytes. The correct representation of osmolarity focuses on how it impacts the osmotic pressure exerted by the solutes in a given volume of liquid.

Understanding that osmolarity includes all particles in solution is key. The other definitions provided in the choices relate to different contexts; for instance, the measure involving moles of solute per kg of solvent refers to molality, which is relevant for certain calculations in physical chemistry. The measure involving moles of solute per liter of H2O might suggest an emphasis on the solvent, but it does not adequately capture the concept of osmolarity as it pertains to the total volume of the solute in the overall solution. The choice referencing moles of solute per volume of gas is unrelated to the concept of osmolarity, which is specifically concerned with liquid solutions.

Therefore, the definition that accurately encapsulates osmolarity considers the total concentration of solute particles within the context of the entire solution.