Solutions

I. Solution Composition
A. Molarity is the number of moles of solute per liter of solution. Mass percent is the percent by mass of the solute in the solution. Mole fraction is the ratio of the number of moles of a given component to the total number of moles of solution. Molality is the number of moles of solute per kilogram of solvent.
B. Normality is defined as the number of equivalents in a soluition. For an acid-base reaction the equivalent is the mass of acid or base that can furnish or accept exactly 1 mole of protons. For oxidation-reduction reactions, the equivalent is defined as the quantity of oxidizing or reducing agent that can accept or furnish 1 mole of electrons.

II. Energies of Solution Formation
A. Enthalpy of Solution is the sum of the DH values for the steps in the formation of a solution. These DH values are for expanding the solute (DH1), expanding the solvent (DH2), and the interaction between the solute and solvent (DH3). The enthalpy of hydration combines the terms DH2 and DH3.
B. Like dissolves like.

III. Factors Affecting Solubility
A. Structure affects solubility when the bonds in a molecule cause it to be polar or non-polar. This makes the molecule soluble in a substance of that polarity.
B. Pressure is directly proportional to the amount of a gas dissolved in a solution. This is equated by Henry's law: P = kC.

IV. The Vapor Pressures of Solutions
A. The presence of a nonvolatile solute reduces the tendency of solvent molecules to escape. A nonvolatile solute has no tendency to escape from solution into the vapor phase. Raoult's law: Psoln = XsolventP0solvent. When there is a solution of two volatile substances a modified version of Raoult's law is used: Psoln = XAP0A + XBP0B. A solution that has attraction or repulsion between components will have a negative or positive deviation from Raoult's law, respectively.

V. Boiling-Point Elevation and Freezing-Point Depression
A. Since the presence of a solute lowers the vapor pressure more heat energy is required for the liquid to change to a gas. Thus, boiling point is elevated by the equation: DT = Kbmsolute.
B. When a solute is present in a solution it interruption the interactions required for freezing to occur. Thus, freezing point is depressed by the equation: DT = Kfmsolute.

VI. Osmotic Pressure
A. A semipermeable membrane allows solvent but not solute molecules to pass through. Osmotic pressure is the pressure needed to stop osmosis. Osmotic pressure is equated: p = MRT.
VII. Van't Hoff Factor i
A. Where the factor = moles of particles in solution divided by the moles of solute dissolved.