Chapter 12 Flashcards
solution
A solution is composed of two parts: the solute and the solvent.
solute
The gas (or solid) in a solution of gases (or solids), or the component present in the smaller amount.
solvent
The liquid in the case of a solution of gases or solids, or the component present in the larger amount.
miscible
Fluids that mix with or dissolve in each other in all proportions
immiscible
Fluids that do not dissolve in each other
saturated solution
is in equilibrium with respect to the amount of dissolved solute.
The rate at which the solute leaves the solid state equals
the rate at which the solute returns to the solid state.
solubility
the amount that dissolves in a given quantity of solvent at a given temperature.
unsaturated solution
is a solution not in equilibrium with respect to a given dissolved substance and in which more of the substance can be dissolved.
supersaturated solution
a solution that contains more dissolved substance than a saturated solution does.
when does a supersaturates solution occuer
when a solution is prepared at a higher temperature and is then slowly cooled. This is a very unstable situation, so any disturbance causes precipitation.
Solubility can be understood in terms of two factors:
- The natural tendency toward disorder favors dissolving
2. The relative forces between and within species must be considered.
Stronger forces within solute species _________ dissolving
oppose
Stronger forces between species _____ dissolving.
favor
“Like dissolves like.”
solutes dissolve in solvents that have the same type of intermolecular forces.
The stronger ion-dipole force between the ion and the solvent—that is, hydration energy—________ dissolving.
favors
A stronger force between ions—that is, lattice energy—_______ dissolving.
opposes
The process of dissolving occurs at the
surfaces of the solid
12 | 14In most cases, solubility increases with increasing temperature. However, for a number of compounds, solubility decreases with increasing temperature. Why?
The difference is explained by differences in the heat of solution.
When dissolving absorbs heat (is endothermic), the temperature of the solution _____ as the solute dissolves
decreases
The solubility will ________ as temperature increases (endothermic)
increase
When dissolving releases heat (is exothermic), the temperature of the solution _________ as the solute dissolves
increases
The solubility will ________ as temperature increases (exothermic)
decrease
Henry’s law
describes the effect of pressure on gas solubility
S = kHP
The solubility of a gas in a liquid is directly proportional to the
partial pressure of the gas above the solution.
In general, pressure has little or no effect on
the solubility of solids or liquids in water.
The solubility of a gas increases as
pressure increases, as illustrated at right.
The concentration of a solute can be quantitatively expressed in several ways:
- Molarity
- Mass percentage of solute
- Molality
- Mole fraction
Molarity
the moles of solute per liter of solution. It is abbreviated as M.
M=moles of solute/liters of solution
Mass percentage of solute
is the percentage by mass of solute in a solution.
mass percentage of solute=grams of solute/grams of solution x 100
Molality
the moles of solute per kilogram of solvent. It is abbreviated as m.
m=moles of solute/kilograms of solvent
Mole fraction
the moles of the component over the total moles of solution. It is abbreviated X
X=moles of solute/total moles of solution
Colligative properties
are properties that depend on the concentration of the solute molecules or ions in solution but not on the chemical identity of the solute
What are the 4 colligative properties
- Vapor-pressure lowering
- Boiling-point elevation
- Freezing-point lowering
- Osmotic pressure
The vapor pressure of a solution, P, is less than the vapor pressure of the
pure solvent, P°.
When the solute is nonvolatile, the vapor pressure of a solution is the
mole fraction of the solvent times the vapor pressure of pure solvent.
To establish an equilibrium (vapor pressure), the gaseous solvent will
condense in the more concentrated solution until the vapor pressures and concentrations are equal.
vapor-pressure lowering is directly proportional to the
solute concentration, the definition of a colligative property
When the solute is nonvolatile,
it has no appreciable vapor pressure itself and forms an ideal solution.
When the solute is volatile
a nonideal solution results.
The boiling point of a solution is higher than the boiling point of
pure solvent
The freezing point of a solution is lower than the freezing point of
Pure solvent
Osmosis
is the phenomenon of solvent flow through a semipermeable membrane to equalize the solute concentration on both sides of the membrane
A semipermeable membrane
allows solvent molecules to pass through but not solute molecules
osmotic pressure, , is equal to the pressure that, when applied,
just stops osmosis. Osmotic pressure is a colligative property of a solution
Correction Factor
Ionic solutes dissolve to form more than one particle per formula unit. We alter the colligative property equations to account for this fact by including i, the number of ions per formula unit
A colloid is a
dispersion of particles of one substance (the dispersed phase) throughout another substance or solution (the continuous phase). The dispersed particles range from 1000 pm to 200,000 pm in size—much larger than single molecules or single ions. (fog is an example)
Colloids exhibit the Tyndall effect.
The path of the light is visible through a colloid because the light is reflected by the relatively larger-sized particles in the dispersed phase.
aerosols
are liquid droplets or solid particles dispersed throughout a gas
emulsion
consists of liquid droplets dispersed throughout another liquid (for example, particles of butterfat dispersed through homogenized milk).
sol
consists of solid particles dispersed in a liquid
Colloids in which the continuous phase is water are categorized into two major classes
hydrophilic colloids and hydrophobic colloids
hydrophilic colloid
A colloid in which there is a strong attraction between the dispersed phase and the continuous phase (water).
hydrophobic colloid
A colloid in which there is a lack of attraction between the dispersed phase and the continuous phase (water).
Coagulation is the process by which the
dispersed phase of a colloid is made to aggregate and thereby separate from the continuous phase. It is analogous to precipitation from a solution.Curdled milk is an example of coagulation
When molecules or ions that have both a hydrophobic end and a hydrophilic end are dispersed in water, they associate, or aggregate, to form colloidal-sized particles called
micelles
A colloid in which the dispersed phase consists of micelles is called an
association colloid
In water solution, the stearate ions associate to form micelles in which
the hydrocarbon ends point inward toward one another and away from the water, and ionic carboxyl groups are on the outside of the micelle facing the water
The cleansing action of soap occurs because
oil and grease can be absorbed into the hydrophobic centers of soap micelles and washed away.
The detergent molecules we have discussed so far are classified in the trade as anionics, because
they have a negative charge at the hydrophilic end
Other detergent molecules are classified as cationics, because
they have a positive charge at the hydrophilic end
