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General Chemistry II > Chapter 13: Solutions > Flashcards

Chapter 13: Solutions Flashcards

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1
Q

what does the addition of a sugar-water solution do to blood’s freezing point

A

the high concentration of glucose in the bloodstream prevents the blood from freezing because concentrated solutions have a lower freezing point than the corresponding pure liquid

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2
Q

are solutions homogeneous or heterogenous

A

homogenous

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3
Q

what is a solution vs a mixture

A

a mixture is made up of two or more different chemical substances

a solution may be composed of different phases of substances

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4
Q

what are the components of a solution

A

solute and solvent

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5
Q

solute and solvent defnnition

A

component that is being dissolved (mixed) into the solvent

usually the major component of a solution is referred to as the solvent, and the minor component is called the solute

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6
Q

what causes solution formation

A

the interaction of the intermolecular forces of solute and solvent particles

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7
Q

what dissolves what? in general

A

like dissolves like

polar-polar
nonpolar-nonpolar

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8
Q

what kind of mixing is more energetically favorable

A

uniform mixing

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9
Q

what kind of mixing does nature have a tendency toward

A

spontaneous mixing

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10
Q

name a gaseous solution, a liquid solution, and a solid solution

A

air
seawater
brass

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11
Q

soluble definition

A

when one substance (solute) dissolves in another (solvent)

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12
Q

insoluble def.

A

when one substance does not dissolve in another

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13
Q

what does solubility depend on

A

Nature’s tendency toward mixing

The types of intermolecular attractive forces

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14
Q

When solutions with different solute concentrations come in contact, what happens?

A

they spontaneously mix to result in a uniform distribution of solute throughout the solution.

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15
Q

The mixing of physical systems leans towards a _____ potential energy

A

lower

However, the formation of a solution does not necessarily lower the potential energy of the system.

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16
Q

When two ideal gases are put into the same container, they spontaneously mix, even if the difference in attractive forces is negligible. why?

A

The gases mix because the energy of the system is lowered through the release of entropy.

As each gas expands to fill the container, it spreads its energy out and lowers its entropy.

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17
Q

entropy

A

the measure of energy dispersal throughout the system

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18
Q

For the solvent and solute to mix, you must overcome what?

A

all of the solute–solute attractive forces; and
some of the solvent–solvent attractive forces.

both processes are endothermic

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19
Q

where does the energy for the solvent and solute to mix come from?

A

At least some of the energy to do this comes from making new solute–solvent attractions, which is an exothermic process.

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20
Q

When the solute-to-solvent attractions are weaker than the sum of the solute-to-solute and solvent-to-solvent attractions, will the solution form?

A

the solution will form only if the energy difference is small enough to be overcome by the increase in entropy from mixing.

21
Q

solubility def.

A

The maximum amount of solute that can be dissolved in a given amount of solvent

22
Q

miscible

A

Two liquids that are mutually soluble

ex. alcohol and water

23
Q

The solubility of one substance in another varies with what?

A

temperature and pressure.

24
Q

when will a chemical dissolve in a solvent (structure)

A

A chemical will dissolve in a solvent if it has a structure similar to that of the solvent.

Also, compatible intermolecular forces

Polar molecules and ionic compounds will be more soluble in polar solvents.

Nonpolar molecules will be more soluble in nonpolar solvents.

25
Q

ΔHsolute is endo or exothermic?

A

Overcome all attractions between the solute particles; therefore, ΔHsolute is endothermic.

26
Q

ΔHsolvent is endo or exothermic?

A

Overcome some attractions between solvent molecules; therefore, ΔHsolvent is endothermic.

27
Q

ΔHmix is endo or exothermic?

A

Form new attractions between solute particles and solvent molecules; therefore, ΔHmix is exothermic.

28
Q

overall ΔH for making a solution, endo or exothermic?

A

The overall ΔH for making a solution depends on the relative sizes of the ΔH for these three processes.

ΔHsoln = ΔHsolute + ΔHsolvent + ΔHmix

29
Q

Solution process

A

Step 1: Separating the solute into its constituent particles

Step 2: Separating the solvent particles from each other to make room for the solute particles

Step 3: Mixing the solute particles with the solvent particles

30
Q

When will a solution be exothemic?

A

If the total energy cost for breaking attractions between particles in the pure solute and pure solvent is less than the energy released in making the new attractions between the solute and solvent

31
Q

When will a solution be endothemic?

A

If the total energy cost for breaking attractions between particles in the pure solute and pure solvent is greater than the energy released in making the new attractions between the solute and solvent

32
Q

heat of hydration def.

A

For aqueous solutions of ionic compounds, the energy added to overcome the attractions between water molecules and the energy released in forming attractions between the water molecules and ions are combined into a term called the heat of hydration.

33
Q

Attractive forces between ions = lattice energy

A

ΔHsolute = –ΔHlattice energy

34
Q

Attractive forces in water are what kind of interaction?

A

H bonds

35
Q

Attractive forces between ion and water are what interactions?

A

ion–dipole

36
Q

ΔHhydration = ?

A

heat released when 1 mol of gaseous ions dissolves in water

= ΔHsolvent + ΔHmix

37
Q

Because the lattice energy is always exothermic, 
the size and sign on the ΔHsoln tells us something 
about ΔHhydration.
what is that?

A

If the heat of solution is large and endothermic, then the amount of energy it costs to separate the ions is more than the energy released from hydrating the ions.

ΔHhydration < ΔHlattice when ΔHsoln is (+)

If the heat of solution is large and exothermic, then the amount of energy it costs to separate the ions is less than the energy released from hydrating the ions.

ΔHhydration > ΔHlattice when ΔHsoln is (−)

38
Q

For an aqueous solution of an ionic compound, the ΔHsolution is the difference between the heat of hydration and the lattice energy.

A

ΔHsolution = ΔHsolute + ΔHsolvent + ΔHmix

ΔHsolution = –ΔHlattice energy + ΔHsolvent + ΔHmix

ΔHsolution = ΔHhydration – ΔHlattice energy

ΔHsolution = –ΔHlattice energy + ΔHhydration

39
Q

what does it mean for ions to be hydrated? and what does this cause?

A

when ions dissolve in water, each ion is surrounded by water molecules

the formation of these ion-dipole attractions causes the heat of hydration to be very exothermic

40
Q

Shortly after some solute is dissolved, solute particles can start to recombine to reform solute molecules., what does this say about the rate of dissolution and deposition?

A

The rate of dissolution is much greater than the rate of deposition, and the solute continues to dissolve.

41
Q

Eventually, the rate of 
dissolution = the rate 
of deposition. what does this mean?

A

The solution is 
saturated with solute 
and no more solute 
will dissolve.

42
Q

what does it mean for a solution to be saturated?

A

the solute and solvent are in dynamic equilibrium

If you add more solute, it will not dissolve.

43
Q

what does the saturation concentration depend on?

A

temperature and pressure of gases

44
Q

what does it mean for a solution to be unsaturated?

A

A solution that has less solute than saturation

more solute will dissolve at this temperature

45
Q

what does it mean for a solution to be supersaturated?

A

A solution that has more solute than saturation

46
Q

what is one method of purification

A

One method of purification involves dissolving a solid in a hot solvent until the solution is saturated.

As the solution slowly cools, the solid crystallizes out, leaving impurities behind.

47
Q

For most solids, the solubility of the solid does what as the temperature increases.

A

solubility increases

48
Q

Gases solubility in water vs. ionic or polar covalent solids

A

Gases generally have lower solubility in water than ionic or polar covalent solids because most are nonpolar molecules.

Usually, gases with high solubility are actually reacting with water.

49
Q

what happens to the solubility of gas as the temperature increases

A

solubility decreases

The ΔHsolution is exothermic because you do not need to overcome solute–solute attractions.

General Chemistry II (2 decks)

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