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CHY 102 > Chemistry midterm 2: Solutions and Colloids > Flashcards

Chemistry midterm 2: Solutions and Colloids Flashcards

1
Q

What is a solution

A

a uniform, homogeneous mixture where solute is present as individual atoms, ions or small molecules

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2
Q

An alloy is

A

solid solution of one metal dissolved in another

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3
Q

What is a solute

A

the least amount component in solution comprised of substances within a solution

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4
Q

What is a solvent

A

the most abundant component in a solution which determines the state of the solution

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5
Q

What is solubility

A

the maximum amount of solute that dissolves in a fixed quantity of solvent at a given temperature

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6
Q

What are some characteristics of solutions

A
  • They are homogeneous; after a solution is mixed, it has the same composition at all points throughout (its composition is uniform)
  • The physical state of a solution—solid, liquid, or gas—is typically the same as that of the solvent
  • The components of a solution are dispersed on a molecular scale; they consist of a mixture of separated
    solute particles (molecules, atoms, and/or ions) each closely surrounded by solvent species
  • The dissolved solute in a solution will not settle out or separate from the solvent
  • The composition of a solution, or the concentrations of its components, can be varied continuously (within limits determined by the solubility of the components
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7
Q

The formation of a solution is an example of what type of process

A

A spontaneous process. a process that occurs under specified conditions without the requirement of energy from some external source

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8
Q

What are two criteria that favour a spontaneous formation of a solution

A
  1. a decrease in the internal energy of the system (an exothermic change)
  2. an increased dispersal of matter in the system (which indicates an increase in the entropy of the system
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9
Q

What is an ideal solution

A
  • When the strengths of the intermolecular forces of attraction between solute and solvent species in a solution
    are no different than those present in the separated components, the solution is formed with no accompanying
    energy change
  • A mixture of ideal gases (or gases such as helium
    and argon, which closely approach ideal behavior) is an example of an ideal solution, since the entities
    comprising these gases experience no significant intermolecular attractions.
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10
Q

What type of attraction plays an important part in the dissolution of ionic compounds in water

A

ion-dipole attraction

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11
Q

What happens when ionic compounds dissolute in water

A

When ionic compounds dissolve in water, the ions in the solid separate and disperse uniformly throughout the
solution because water molecules surround and solvate the ions, reducing the strong electrostatic forces between them. This process represents a physical change known as dissociation

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12
Q

What happens when KCl is added to water

A

Ion-dipole forces attract the positive (hydrogen) end of the polar water molecules to the negative chloride ions at the surface of the solid, and they attract the negative (oxygen) ends to the positive potassium ions. The water molecules surround individual K+ and Cl− ions, reducing the strong interionic forces that bind the ions together and letting them
move off into solution as solvated ion

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13
Q

What are miscible fluids

A

dissolve in all proportions

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14
Q

What are immiscible fluids

A

do not mix; form layers

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15
Q

What is a saturated solution

A
  • When a solute’s concentration is equal to its solubility
  • Suppose we place some solute in a container of solvent. Some solute dissolves, solution concentration increases for some time. Eventually, the concentration remains constant
  • At this point the solution is said to be saturated. No more solute will go into solution
  • rate of dissolution is equal to the rate of deposition
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16
Q

What is an unsaturated solution

A
  • If the solute’s concentration is less than its solubility
  • rate of dissolution is greater than the rate of deposition; more solute is capable of dissolving
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17
Q

What is a supersaturated solution?

A
  • there is more solute dissolved than the equilibrium amount, the solution is unstable and solid will spontaneously precipitate out
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18
Q

When is dynamic equilibrium reached

A
  • when solute molecules dissolve and recrystallize at the same rate.
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19
Q

What happens in solutions of gases and liquids

A

The solubility of a gas in a liquid is affected by the intermolecular attractive forces between solute and solvent species. Unlike solid and liquid solutes, however, there is no solute-solute intermolecular attraction to overcome when a gaseous solute dissolves in a liquid solvent since the atoms or molecules comprising a gas are far separated and experience negligible interactions. Consequently, solute solvent interactions are the sole energetic factor affecting solubility

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20
Q

The solubility of most solids increases with

A

temperature (some exceptions).

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21
Q

The solubility of gases increases with

A

decrease in temperature (inverse relationship), and pressure increase

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22
Q

What is recrystallization

A

purification technique that slowly cools a saturated solution to form pure crystals of the solute. Impurities are unsaturated and do not crystallize.

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23
Q

What is fractional crystallization

A

The separation of a mixture of substances into pure components on the basis of their differing solubilities.

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24
Q

Pure A has only A-A interactions, pure B has only B-B interactions, what will the solution have

A

Solution of A and B has A-A, B-B and A-B interactions

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25
Q

Substances that exhibit similar types of intermolecular
force will

A

dissolve in each other: “like dissolves in like.”

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26
Q

non-polar molecules are soluble in

A

non-polar solvents

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27
Q

Polar molecules are soluble in

A

polar substances

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28
Q

Ionic compounds are soluble in

A

Polar solvents

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29
Q

Which particles oppose solubility

A

Charge density and delta H(solute): high charge density opposed solubility

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30
Q

Which particles tend to be soluble

A

Low charge density salts

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31
Q

How can the temperature dependence of solubility can be exploited to prepare supersaturated solutions of certain
compounds

A

A solution may be saturated with the compound at an elevated temperature (where the solute is
more soluble) and subsequently cooled to a lower temperature without precipitating the solute. The resultant
solution contains solute at a concentration greater than its equilibrium solubility at the lower temperature (i.e.,
it is supersaturated) and is relatively stable. Precipitation of the excess solute can be initiated by adding a seed
crystal (see the video in the Link to Learning earlier in this module) or by mechanically agitating the solution

32
Q

What prevents oil from dissolving in water

A

strong water-water interactions

33
Q

When ionic solutions dissolve, the ion-ion force changes to

A

ion-dipole force

34
Q

How do ion-dipole forces orient a molecule

A

Ion-dipole forces orient water molecules around an ion. In
the innermost hydration or solvation shell here, six water
molecules surround the cation octahedrally.
Dissolved ions and their solvated shell of water molecules
can move as intact entities when an electric field is applied

35
Q

What are electrolytes

A

The solutions formed from ionic species are conductors of electricity

36
Q

What is solavation

A

the process of surrounding a particle with solvent particles. In water, solvation is called hydration

37
Q

The hydration of an ion is always

A

exothermic because ion-dipole forces are very strong

38
Q

High charges and small ionic radius contribute to

A

strong heats of hydration. Heats of hydration decrease down a group and increase across a group

39
Q

high charges and small ionic radii also result in

A

High lattice energies

40
Q

When a solution forms, solute-solute attractions and solvent-solvent attractions are replaced by

A

Solute-solvent attractions. This can only occur if the forces within the solute and solvent are similar to the forces that replace them.

41
Q

What are driving forces of dissolution

A
  • Tendency towards greater disorder
  • Minimizing potential energy (enthalpy), minimizing attractive forces
42
Q

Gas solubility can be characterized by which law

A

Henry’s Law. Gases are more soluble in water as
pressure increases

43
Q

Descibe suba driving and “The Narcs”

A
  • Deep-sea divers breathe high pressure air underwater
  • Dissolved Nitrogen at depths of 25 – 40 m caused intoxication
  • This condition is often called “The Narcs” or “”Rapture of the Deep”
44
Q

Describe solubility of CO2 in carbonated drinks

A
  • Solubility of CO2 in water is high under high pressure
  • Opening a bottle relieves the pressure, solubility decreases.
  • CO2 evaporates from solution as fizz
45
Q

Describe scuba diving and “The Bends”

A
  • Deep-sea divers breathe high pressure air underwater
  • Excess N2 dissolves in the blood
  • A rapid return to the surface causes N2 to diffuse out of the blood
  • This painful and often dangerous condition is called “the Bends”
46
Q

What are colligative properties

A

There are a few solution properties, however, that depend
only upon the total concentration of solute species, regardless of their identities. These colligative properties
include vapor pressure lowering, boiling point elevation, freezing point depression, and osmotic pressure.

47
Q

What are colligative properties

A

properties that depend on the relative amounts of solute and solvent and are independent of the chemical identity of the solute

48
Q

What are electrolytes

A

separate into ions when it dissolves (ionic compounds)

49
Q

What are non-electrolytes

A

does not dissociate to form ions (molecules)

50
Q

What are extensive properties

A

depend on the quantity of matter (in atoms), volume, and mass whereas intensive properties are independent of the quantity of matter, density, and temperature. Colligative is a new third category

51
Q

The French scientist Francois-Marie Raoult, discovered

A

that, at any temperature, the vapor pressure of a solvent is proportional to its mole fraction in a solution

52
Q

What is Raoult’s law

A

The partial pressure exerted by any component of an ideal solution is equal to the vapor pressure of the pure component multiplied by its mole fraction in the solution.

53
Q

According to Raoult’s law, when two volatile liquids A and B are mixed,

A
  • the total vapour pressure is above the mixture is the sum of the vapour pressures of the two components
54
Q

For a volatile nonelectrolyte, the vapour of the solution
contains

A

both solute and solvent.

55
Q

What is fractional distillation

A

method of separating volatile liquids from one another

56
Q

Describe process of distillation

A
  1. Start by heating the solution to its boiling point
  2. Collect the vapour which is richer in the more volatile compound
  3. Cool and condense the vapour to a liquid
  4. Repeat until desired purity is reached
57
Q

What are Azeotropes

A

liquid mixtures that we are unable to separate by distillation

58
Q

What is boiling point elevation

A

The increase in boiling point observed when nonvolatile solute is dissolved in a solvent, ΔTb, is
called boiling point elevation and is directly proportional to the molal concentration of solute species

59
Q

Boiling point elevation constants are characteristic properties that depend on the identity of the

A

Solvent

60
Q

What is the freezing point depression

A

The decrease in freezing point of a dilute solution compared to that of the pure solvent, ΔTf, is called the
freezing point depression and is directly proportional to the molal concentration of the solute

61
Q

What is activity

A

the “effective concentration” of a species, as measured by colligative properties

62
Q

What is osmosis

A

the movement of solvent particles from a region of higher to a region of lower concentration through a semipermeable
membrane

63
Q

Solvent will always flow from a

A

more dilute solution to a more concentrated one

64
Q

Osmotic pressure is

A

the pressure that must be applied to prevent the net flow of solvent

65
Q

Describe osmotic pressure and red blood cells

A
  • A red blood cell in an isotonic solution has its normal
    shape.
  • A hypotonic solution has a lower concentration of particles than the cell. A cell in a hypotonic solution absorbs water and swells until it bursts
  • A hypertonic solution has a higher concentration of
    dissolved particles than the cell. If a cell is placed in
    a hypertonic solution, water moves out of the cell,
    causing it to shrink
66
Q

What is isotonic solution

A

of equal osmotic pressure

67
Q

What is a hypertonic solution

A

of greater osmotic pressure

68
Q

A strong electrolyte dissociates

A

completely to form ions. Each mole of solute gives more than 1 mol of dissolved particles

69
Q

The formula of the compound indicates

A

the expected number of particles in solution

70
Q

The van’t Hoff factor takes into account

A

the dissociation of a strong electrolyte to predict the effect on the solution

71
Q

What is reverse Osmosis

A
  • Sea water can be desalinated by “reverse osmosis,”
  • P applied to hypertonic side: Forces pure water through membrane, Need P must be > Π
72
Q

For colloids, the particulate component typically present in a relatively minor amount is called

A

Dispersed phase

73
Q

For colloids, the substance or solution throughout which the particulate is dispersed is called the

A

Dispersion medium

74
Q

Colloids may involve virtually any combination of

A

physical states (gas in liquid, liquid in solid, solid in gas, etc.)

75
Q

Particles of colloidal size are formed by two methods, they are:

A
  1. Dispersion methods: breaking down larger particles. For example, paint pigments are produced by dispersing large particles by grinding in special mills.
  2. Condensation methods: growth from smaller units, such as molecules or ions. For example, clouds form when water molecules condense and form very small droplets
76
Q

How can an emulsion be prepared

A

by shaking together or blending two immiscible liquids. This breaks one liquid into droplets of colloidal size, which then disperse throughout the other liquid. Oil spills in the ocean may be difficult to clean up, partly because wave action can cause the oil and water to form an emulsion

77
Q

What is an emulsifying agent

A

a substance that inhibits the coalescence of the dispersed liquid. For example, a little soap will stabilize an emulsion of kerosene in water.

CHY 102 (6 decks)

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