C. Molarity is the number of moles of solute in one liter of solution. M is useful when the quantity of solute participating in a chemical rxn taking place in soln is of interest. M can vary with T bec soln volume varies with T. D. Molality is the conc of a soln expressed in moles of solute per kg of solvent. There's usually a limit to the amt of solute that can be dissolved in a solvent. 15-3 A. Dissolving takes place at the surface of a solid.
Solvation is called hydration when the solvent is water.
If breaking attractions requires more E than is released in forming attractions, the soln process will be endothermic. If breaking attraction requires less E than is released forming attractions, the soln process will be exothermic. Factors affecting the rate of dissolving a. increasing the surface area of the solute - when a solid dissolves in a liquid the molecules or ions of the solute are attracted away the surface and into soln. In general the more finely divided a substance is the greater the surface area per unit mass and the more quickly it will dissolve. Stirring or shaking helps to disperse the solute particles and brings fresh solvent into contact with the surface.