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MBBCh 1- CHEM1048A > Properties of Solutions > Flashcards

Properties of Solutions Flashcards

1
Q

What is a solution?

A

Solutions are homogeneous mixtures of two or more pure substances.

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2
Q

In a solution, the _____ is dispersed uniformly throughout the ____.

A

solute

solvent

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3
Q

The solute is(are) the substance(s) present in the ____ amount(s)

The solvent is the substance present in the ____ amount

A

smaller

larger

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4
Q

Solutes and solvent are components of the _____.

A

solution

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5
Q

• The ability of substances to form solutions depends on : (2)

A

– Natural tendency towards mixing

– Intermolecular forces

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6
Q
  • Mixing of gases is a _____ process.

* Each gas acts as if it is alone to fill the container.

A

spontaneous

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7
Q

What does mixing cause? (2)

A
  • Mixing causes more randomness in the position of the molecules, increasing a thermodynamic quantity called entropy.
  • The formation of solutions is favoured by the increase in entropy that accompanies mixing.
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8
Q

Any intermolecular force of attraction can be the _____ between solute and solvent molecules.

A

attraction

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9
Q
  • ____-_____ interactions must be overcome to disperse these particles when making a solution.
  • ____-_____ interactions must be overcome to make room for the solute.
  • _____-______ interactions occur as the particles mix.
A
  • Solute-solute
  • Solvent-solvent
  • Solvent-solute
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10
Q

What must the strength of the intermolecular forces be?

A

The intermolecular forces between solute and solvent particles must be strong enough to compete with those between solute particles and those between solvent particles.

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11
Q

What is solubility?

A

• Solubility is the maximum amount of solute that can dissolve in a given amount of solvent at a given temperature.

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12
Q
  • _____ solutions have that amount of solute dissolved.

* _____ solutions have any amount of solute less than the maximum amount dissolved in the solution.

A

Saturated

Unsaturated

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13
Q

What is a saturated solution?

A

– In a saturated solution, the solvent holds as much solute as is possible at that temperature.
– Dissolved solute is in dynamic equilibrium with solid solute particles.

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14
Q

What is an unsaturated solution?

A

– If a solution is unsaturated, less solute can dissolve in the solvent at that temperature is dissolved in the solvent.

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15
Q

What is a supersaturated solution? (2)

A

– In supersaturated solutions, the solvent holds more solute than is normally possible at that temperature.
– These solutions are unstable; crystallization can usually be stimulated by adding a “seedcrystal”or scratching the side of the flask.

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16
Q

• Chemists use the axiom “like dissolves like.” What does this mean? (2)

A

– Polar substances tend to dissolve in polar solvents.

– Nonpolar substances tend to dissolve in nonpolar solvents.

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17
Q

What does the solubility of gases in water increase with? (3)

A
  • Solubility of gases in water increases with molecular mass.
  • The attractive forces between the gas molecules and solvent molecules is mainly dispersion forces.
  • These increase with increasing size and molecular mass.
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18
Q

• The more similar the ______ attractions, the more likely one substance is to be soluble in another.

A
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19
Q

Glucose (which has_____ ______) is very soluble in water, while cyclohexane (which only has dispersion forces) is not.

A

hydrogen bonding

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20
Q

True or false,

The solubility of gases in water increases with increasing mass

A
  • In general, the solubility of gases in water increases with increasing mass.
  • Larger molecules have stronger dispersion forces.
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21
Q

What is the relationship between gases in a liquid and pressure?

A
  • The solubility of liquids and solids does not change appreciably with pressure.
  • But the solubility of a gas in a liquid is directly proportional to its pressure.
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22
Q

What is Henry’s Law?

A
  • The solubility of a gas is proportional to the partial pressure of the gas above the solution.
  • The amount of gas dissolved in a solution is directly proportional to the pressure of the gas above the solution.
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23
Q

Sg = kPg where, (3)

A
  • Sg is the solubility of the gas,
  • k is the Henry’s Law constant for that gas in that solvent, and
  • Pg is the partial pressure of the gas above the liquid.
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24
Q

• Sg is usually expressed as _____.

A

molarity

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25
Q

What does Henry’s law constant depend on?

A

• Henry’s law constant depends on the solute, solvent and temperature.

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26
Q

What is an application of Henry’s Law?

A

> When a scuba diver dives, the increased pressure causes N2(g) to dissolve in the blood.
If a diver rises too fast, the dissolved N2 will form bubbles in the blood, a dangerous and painful condition called “the bends”.
Helium, which does not dissolve in the blood, is mixed with O2 to prepare breathing mixtures for deep descents.

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27
Q

How do blood gases act? (2)

A

> In the lungs, O2 enters the blood, while CO2 from the blood is released.
In the tissues, O2 enters the cells, which release CO2 into the blood.

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28
Q

_____ blood gas test or a blood gas analysis measures oxygen and carbon dioxide levels in the blood.

A

Arterial

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29
Q

How do blood gasses flow into and out of tissues? (2_

A

In the body,
• O2 flows into the tissues because the partial pressure of O2 is higher in blood, and lower in the tissues.
• CO2 flows out of the tissues because the partial pressure of CO2 is higher in the tissues, and lower in the blood.

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30
Q

• Generally, the solubility of solid solutes in liquid solvents increases with increasing ____.

A

temperature

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31
Q

True or false,

• Generally, the solubility of gases in liquid solvents decreases with increasing temperature.

A

True,
– Carbonated soft drinks are more “bubbly” if stored in the refrigerator.
– Warm lakes have less O2 dissolved in them than cool lakes.

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32
Q

What is concentration?

A

> Concentration – a term used by scientists to designate the amount of solute dissolved in a given quantity of solvent or quantity of solution.
The more solute is dissolved in a certain amount of solvent, the more concentrated the resulting solution.

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33
Q

What is molarity?

A

Molarity (M), or molar concentration, is defined as the number of moles of solute per liter of solution.

molarity = moles solute/liters solution

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34
Q

What is a standard solution?

A

A standard solution –is a solution containing a precisely known concentration of an element or substance.

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35
Q

A known weight of _____ is dissolved to make a specific volume.
> Standard solutions are used to determine the concentration of other solutions, for example in
_______.

A

solute

titrations

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36
Q

Preparing a Standard Solution. (8)

A
37
Q

What are electrolytes?

A
  • The molecules of a chemical compound in solution may dissociate into particles known as ions, which carry an electric charge “electrolytes” e.g. sodium chloride in body fluids.
  • Sodium chloride in solution provides Na+ and Cl- ions, which carry electric charges.
38
Q

Electrolyte ions in the blood plasma include:

A

– the cations K+, Na +, Ca 2+, and Mg 2+.

– the anions Cl-, HCO3-, HPO42-, SO42-, organic acids- and proteins-.

39
Q

Electrolytes in body fluids play an important role in: (3)

A

– maintaining the acid-base balance in the body.
– controlling body water volumes.
– regulating body metabolism.

40
Q

Electrolyte preparations are used in the treatment of _______ in the electrolyte and fluid balance in the body.

A

disturbances

41
Q

Clinically electrolytes, they are provided in the form of: (4)

A

– oral solutions and syrups
– dry granules to be dissolved to make oral solutions
– oral tablets and capsules
– intravenous infusions

42
Q

A concentration unit of ______ per liter is used to express the concentration of electrolytes in
solution.

1000 mEq = 1 Eq

A

milliequivalents

43
Q

• Ionic solutions have a _____ in the number of positive and negative charges present because the dissolving ionic compounds have no net charge.

A

balance

44
Q

How do you express the concentration of electrolytes?

A
45
Q

What is dilution?

A

Dilution is the process of preparing a less concentrated solution from a more concentrated one.

moles of solute before dilution = moles of solute after dilution

46
Q
  • Preparation of a desired solution by adding water to a concentrate.
  • Moles of ____ remains the same.
A

solute

47
Q

Preparation of a dilute solution from a stock solution. (3)

A
48
Q
  1. Mass percent =
A

Mass % of A = mass of A in solution / total mass of solution x 100

49
Q

How else can you express concentration?

A
50
Q

What is a mole fraction?

A

XA+ moles of A/ total moles of all components

51
Q

• Mole fractions have no ____.
• Sum of the mole fractions of all the components in a solution must be equal to __.
• Mole fractions are very useful when dealing with gases, but have limited use when dealing
with ____ solutions.

A

units.
1
liquid

52
Q

What is molality?

A

m= moles of solute/kilograms of solvent

> Since both moles and mass do not change with temperature, molality (unlike molarity) is not temperature-dependent.

53
Q

What is Osmolality?

A
  • Number of osmoles of solute per kg of solvent (water).

* (Osmole is the number of moles of solute that contributes to the osmotic pressure of a solution)

54
Q

Urine osmolality can vary in a healthy person from __-____ mOsm/kg H2O

A

80 -1200

55
Q

The most important osmols in the urine are cations___,___,___ with their corresponding anions as well as urea and glucose.

It is measured by an ______.

A

Na+ , K+ ,NH4+

osmometer

56
Q
  • The primary solutes that are measured in the clinical lab that contribute to the plasma osmolality are sodium, glucose and urea
  • The following formula can obtain therefore an approximation of the plasma osmolality:
A
57
Q
  • Normal serum osmolality is maintained between ___-___ mosm/kg water
  • Under normal conditions the osmolar contributions of glucose and urea are less than 10 mOsm/kg water; thus plasma sodium is the primary determinant of osmolality.
A

280-290

58
Q

What is measured osmolality higher than?

A

Measured osmolality is typically higher than calculated osmolality due to the presence of unmeasured osmoles in plasma (e.g. phosphate, sulfate, amino acids, calcium, etc.)

59
Q

The difference between the measured and calculated
osmolality is termed the osmolar ___
– The osmolar ___ is normally <10mosm/L

A

gap

gap

60
Q

If we know the density of the solution, we can calculate the molality from the ____, and vice versa.

A

molarity

61
Q

What do changes in colligative properties depend on?

A

• Changes in colligative properties depend only on the number of solute particles present, not on the identity of the solute particles.

62
Q

Among colligative properties are: (4)

A

– vapour-pressure lowering
– Boiling-point elevation
– Melting-point depression
– Osmotic pressure

63
Q

How is vapour pressure affected?

A
64
Q

Why is the vapour pressure of a solution lower than that of a pure solvent? (3)

A

> Because of solute-solvent intermolecular attraction, higher concentrations of nonvolatile solutes make it harder for the solvent to escape to the vapour phase.
Therefore, the vapour pressure of a solution is lower than that of the pure solvent.
The amount of vapour pressure lowering depends on the amount of solute.

65
Q

What is Raoult’s Law?

A

Quantifies the extent to which non-volatile solute lowers the vapour pressure of the solvent.

66
Q

What is the formula for Raoult’s law?

A

Note: This is one of those times when you want to make sure you have the vapour pressure of the
solvent.

67
Q

Ideal solution:

A

Ideal solution: one that obeys Raoult’slaw.

68
Q

When does Raoult’s Law break down?

A

• Raoult’s law breaks down when the solvent-solvent and solute-solute intermolecular forces are greater than solute-solvent intermolecular forces.

69
Q

What is Raoult’s law for two components that are volatile?

A

• The component that is more volatile will have higher partial pressure.

70
Q

> Non-volatile solute-solvent interactions also cause solutions to have _____ boiling points and _____ freezing points than the pure solvent.

A

higher

lower

71
Q

Goal: interpret the phase diagram for a solution.

Non-volatile solute lowers the ____ ____. Therefore the triple point - critical point curve is lowered.

A

vapour pressure

72
Q

• The change in boiling point is proportional to the molality of the solution:

A

where Kb is the molal boiling-point elevation constant, a property of the solvent, m is the molality; ΔTb change in bpt

73
Q

ΔTb is added to the normal boiling point of the solvent. Tb = ________

A

Tb = normal boiling point + ΔTb

74
Q

At 1 atm (normal boiling point of pure liquid) there is no _____ by definition.

A

depression

75
Q

What happens when a solution freezes? (2)

A

• When a solution freezes, almost pure solvent is formed first.
– Therefore, the sublimation curve for the pure solvent is the same as for the solution.
– Therefore, the triple point occurs at a lower temperature because of the lower vapour pressure for the solution.

76
Q

The melting-point (freezing-point) curve is a _____ line from the triple point.

A

vertical

77
Q

• The solution freezes at a lower temperature (ΔTf) than the ___ solvent.

A

pure

78
Q

_______ in freezing point (ΔTf) is directly proportional to molality (Kf is the molal freezing-point-depression constant)

A

Decrease

79
Q

• The change in freezing point can be found similarly:

A

• Here Kf is the molal freezing-point depression constant of the solvent.

△Tf is subtracted from the normal freezing point of the solvent.

80
Q

Note that in both equations, △T does not depend on what the solute is, but only on how many particles are dissolved.

Tb =
Tf =

A 
Tb = normal boiling point + ΔTb
Tf = normal freezing point –ΔTf
81
Q
  • Some substances form ____ _____ membranes, allowing some smaller particles to pass through, but blocking other larger particles.
  • In biological systems, most semipermeable membranes allow water to pass through, but solutes are not free to do so.
A

semipermeable

82
Q

What happens in osmosis?

A

> In osmosis, there is the net movement of solvent from the area of higher solvent concentration (lower solute concentration) to the area of lower solvent concentration (higher solute concentration).

83
Q

The pressure required to stop osmosis is known as osmotic pressure, π, calculated as follows:

A
84
Q

If the osmotic pressure is the same on both sides of a membrane (i.e., the concentrations are the same), the solutions are _____.

A

isotonic

85
Q
  • If the solute concentration outside the cell is greater than that inside the cell, the solution is _____.
  • Water will flow out of the cell, and _____ results.
  • If the solute concentration outside the cell is less than that inside the cell, the solution is _____.
  • Water will flow into the cell, and _____ results.
A

hypertonic
crenation
hypotonic
hemolysis

86
Q

What is Osmolarity?

A

• Osmolarity –osmotic concentration is the measure of solute concentration, defined as the total number of osmoles of solute per litre of solution. [Osm/L] or [osmol/L].

87
Q

What is Osmolality?

A

• Osmolality –osmotic concentration is the measure of solute concentration, defined as the total number of osmoles of solute per kilogram of solvent [Osm/kg] or [osmol/kg].

88
Q

We can use the effects of a _____ property such as osmotic pressure to determine the molar mass of a
compound.

A

colligative

89
Q

The van’t Hoff factor (i) is defined as the ratio of solute particles in solution to the number of formula units dissolved:

A

MBBCh 1- CHEM1048A (8 decks)

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