Chapter 4 Physiochemcial Properties of Solutions Conceptrs

define solute and solvent

solute- minor component that is homogeneously dispersed as molecules or ions throughout the solvent. dissolved in solvent

solvent- major component that determines the phase of the solution and present in greater amount

define non electrolyte and electrolyte

nonelectrolyte- substances that do not yield ions when dissolved in water and therefore do not conduct an electric current through the solution

electrolytes- substances that form ions in a solution, conduct an electric current and demonstrate atypical changes in colligative properties

define ideal vs non-ideal solutions

ideal- a solution in which there is no change in the properties of the components of the solution, other than dilution, when they are mixed to form the solution (no heat evolved or absorbed)

non-ideal- heat often absorbed or evolved; vol will be different than just added

for an ideal solution to exist what needs to happen

strengths of attractive forces between the solute and solvent must be identical to the strengths of the attractive forces between the solute-solute, and solvent-solvent

positive vs negative deviation

positive deviation- vapor pressure is greater than expected ( the interaction between A and B molecules is less than that between molecules of the pure constituents)

negative deviation- adhesive attraction between molecules of different species exceeds the cohesive attraction of like molecules resulting in less than expected vapor pressure

define molarity, molality, and mole fraction

molarity- number of moles of solute contained in 1000mL of solution or 1 L

molality- number of moles of solute contained in 1000g or 1kg of solvent

mole fraction- ratio of # of moles of one component of a solution to sum of # of moles of all components with no units

define a constitutive property

depends on structural arrangement of the individual atoms or functional groups of the molecules

includes viscosity, surface tension, vapor pressure, freezing point, boiling point

define colligative properties

depend mainly on the number of particles in a solution

include vapor pressure lowering, freezing point depression, boiling point elevation, and osmotic pressure

colligative property- vapor pressure lowering

when a nonvolatile solute (solid) is combined with a volatile solvent it alters the ability of the solvent molecules to escape from the surface

vapor pressure decreases when dissolving solid in liquid

colligative property- boiling point elevation

as discussed, vp is reduced when a solute is added to the solvent

therefore the solution must be heated to a higher temp for the vapor pressure to reach atmospheric pressure

colligative property- freezing point depression

when a solute is added to a solvent, a decrease in freezing point occurs in proportion to concentration of solute

must be cooled to a lower temp for solvent to overcome obstacles of solute and lock into place

colligative properties- osmotic pressure

measure of the tendency of water to move into one solution from another by osmosis

when solute particles are added to one side of a container, water will start to flow into it, so its level will go up at this side and down at other side

define vapor pressure

the equilibrium pressure of a vapor above its liquid or solid state in a closed system

describe Raoults Law (describes how vapor pressure changes when a solute is added)

the partial vapor pressure of each volatile component in a solution is equal to the pure vapor pressure times its mole fraction

as such, the total vapor pressure can be calculated as the sum of the vapor pressures of the components of the solution