Chapter 13 - Properties of Solutions Flashcards
Define solutions.
homogeneous mixtures of two or more pure substances
Define solute.
the minor component in a solution; dissolved in the solvent
Define solvent.
a substance that dissolves a solute, resulting in a solution
What does the ability of substances to form solutions depend on?
natural tendency toward mixing, intermolecular forces
How is the mixing of gases a spontaneous process?
each gas acts as if it is alone to fill the container
How does mixing increase entropy?
it causes more randomness in the position of molecules
How is the formation of solutions affected by mixing?
it is favored by the increase in entropy which accompanies it
Which intermolecular force of attraction exists between solute and solvent?
any of the intermolecular forces of attraction can exist between solute and solvent molecules
What must happen to solute-solute interactions when making a solution?
solute-solute interactions must be overcome
What must happen to solvent-solvent interactions when making a solution?
solvent-solvent interactions must be overcome
When do solvent-solute interactions occur?
solvent-solute interactions occur as the particles in a solution mix
What must be true for a reaction to occur?
ΔHmix must be close to the sum of ΔHsolute and ΔHsolvent
If a substance disappears when it comes in contact with a solvent, has it definitely dissolved?
no, it may have reacted
What is the opposing process to solution-making?
crystalization
What is true of a saturated solution?
When the rate of the opposing processes is equal, additional solute will not dissolve unless some crystallizes from solution.
What is true of an unsaturated solution?
If we have not yet reached the amount that will result in crystallization, we have an unsaturated solution.
Define solubility.
the maximum amount of solute that can dissolve in a given amount of solvent at a given temperature
What is true of a supersaturated solution?
In supersaturated solutions, the solvent holds more solute than is normally possible at that temperature.
How can crystallization be stimulated in a supersaturated solution?
by adding a “seed crystal” or scratching the side of the flask
Supersaturated solutions are (common/uncommon) solutions.
uncommon
List three factors that affect solubility.
- solute-solvent interactions
- pressure (for gaseous solutes)
- temperature
The (stronger/weaker) the solute-solvent interaction, the (greater/less) the solubility of a solute in a solvent.
stronger, greater
The (larger/smaller) the gas, the (more/less) soluble it will be in water.
larger, more
Polar organic molecules dissolve in water (better/worse) then nonpolar organic molecules.
better
Hydrogen bonding (increases/decreases) solubility, since C-C and C-C (are/are not) very polar.
increases, are
Define miscible.
liquids that mix in all proportions
Define immiscible.
liquids that do not mix in one another
Because hexane is nonpolar and water is polar, they are (miscible/immiscible).
immiscible
What is the biological significance of solubility?
Fat soluble vitamins are nonpolar and are readily stored in fatty tissue of the body; water soluble vitamins need to be included in the daily diet.
The solubility of solids and liquids (are/are not) appreciably affected by pressure.
are not
Gas solubility (is/is not) affected by pressure.
is
What relationship does Henry’s Law describe?
the solubility of a gas is proportional to the partial pressure of the gas above the solution
For (all/most/no) solids, as temperature increases, solubility increases.
most
For (all/most/no) gases, as temperature increases, solubility decreases.
all
List six units of concentration used for solutions.
- Mass percentage
- Parts per million (ppm)
- Parts per billion (ppb)
- Mole fraction
- Molarity
- Molality
How is mass percentage calculated?
the ratio of the mass of the solute to the total solution mass, multiplied by 100
How is parts per million calculated?
the ratio of the mass of the solute to the total solution mass, multiplied by 10^6
How is parts per billion calculated?
the ratio of the mass of the solute to the total solution mass, multiplied by 10^9
How is mole fraction calculated?
the ratio of moles of a substance to the total number of moles in a solution
How is molarity calculated?
the ratio of moles of solute to the total liters of solution
How is molality calculated?
the ratio of moles of solute to the total kilograms of solvent
Molality (does/does not) vary with temperature.
does not
Molarity (does/does not) vary with temperature.
does
What must be used to convert between molality and molarity?
the density of the solution
What do colligative properties depend on?
the quantity of the solute particles
List four colligative properties.
- Vapor-pressure lowering
- Boiling-point elevation
- Freezing-point depression
- Osmotic pressure
The vapor pressure of a solution is (higher/lower) then that of the pure solvent.
lower
What relationship does Raoult’s Law describe?
The vapor pressure of a volatile solvent over the solution is the product of the mole fraction of the solvent times the vapor pressure of the pure solvent.
In ideal solutions, it (is/is not) assumed that each substance will follow Raoult’s Law.
is
Why is boiling point raised in solutions?
vapor pressures are lowered
What happens to the freezing point of a solution as the boiling point is raised?
the freezing point is lowered
What is the relationship between boiling point elevations/freezing point depression and molality?
The change in temperature is directly proportional to molality.
What does the van’t Hoff Factor describe?
it takes into account dissociation in solution
Define semipermeable membrane.
a membrane that allows some smaller particles to pass through but blocks larger particles
Define osmosis.
the net movement of solvent molecules from solution of low to high concentration across a semipermeable membrane
Define osmotic pressure.
the applied pressure to stop osmosis
If two solutions seperated by a semipermeable membrane have (the same/different) osmotic pressure, no osmosis will occure.
the same
Define colloid suspension.
a suspension of particles larger then individual ions or molecules but too small to be settled out by gravity
Define Tyndall effect.
the ability of colloid suspensions to scatter rays of light
What does an emulsifier do?
it causes something that does not normally dissolve in a solvent to do so
Define Brownian Motion.
motion of colloids due to numerous collisions with the much smaller solvent
