Properties of Solutions Flashcards
1
Q
What is a solution?
A
Solutions are homogeneous mixtures of two or more pure substances.
2
Q
In a solution, the _____ is dispersed uniformly throughout the ____.
A
solute
solvent
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
4
Q
Solutes and solvent are components of the _____.
A
solution
5
Q
• The ability of substances to form solutions depends on : (2)
A
– Natural tendency towards mixing
– Intermolecular forces
6
Q
- Mixing of gases is a _____ process.
* Each gas acts as if it is alone to fill the container.
A
spontaneous
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.
8
Q
Any intermolecular force of attraction can be the _____ between solute and solvent molecules.
A
attraction
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
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.
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.
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
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.
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.
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.
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.
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.
18
Q
• The more similar the ______ attractions, the more likely one substance is to be soluble in another.
A
19
Q
Glucose (which has_____ ______) is very soluble in water, while cyclohexane (which only has dispersion forces) is not.
A
hydrogen bonding
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.
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.
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.
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.
24
Q
• Sg is usually expressed as _____.
A
molarity
25
What does Henry's law constant depend on?
• Henry’s law constant depends on the solute, solvent and temperature.
26
What is an application of Henry's Law?
> 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.
27
How do blood gases act? (2)
> 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.
28
_____ blood gas test or a blood gas analysis measures oxygen and carbon dioxide levels in the blood.
Arterial
29
How do blood gasses flow into and out of tissues? (2_
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.
30
• Generally, the solubility of solid solutes in liquid solvents increases with increasing ____.
temperature
31
True or false,
| • Generally, the solubility of gases in liquid solvents decreases with increasing temperature.
True,
– Carbonated soft drinks are more “bubbly” if stored in the refrigerator.
– Warm lakes have less O2 dissolved in them than cool lakes.
32
What is concentration?
> 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.
33
What is molarity?
Molarity (M), or molar concentration, is defined as the number of moles of solute per liter of solution.
molarity = moles solute/liters solution
34
What is a standard solution?
A standard solution –is a solution containing a precisely known concentration of an element or substance.
35
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
_______.
solute
| titrations
36
Preparing a Standard Solution. (8)
37
What are electrolytes?
* 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
Electrolyte ions in the blood plasma include:
– the cations K+, Na +, Ca 2+, and Mg 2+.
| – the anions Cl-, HCO3-, HPO42-, SO42-, organic acids- and proteins-.
39
Electrolytes in body fluids play an important role in: (3)
– maintaining the acid-base balance in the body.
– controlling body water volumes.
– regulating body metabolism.
40
Electrolyte preparations are used in the treatment of _______ in the electrolyte and fluid balance in the body.
disturbances
41
Clinically electrolytes, they are provided in the form of: (4)
– oral solutions and syrups
– dry granules to be dissolved to make oral solutions
– oral tablets and capsules
– intravenous infusions
42
A concentration unit of ______ per liter is used to express the concentration of electrolytes in
solution.
1000 mEq = 1 Eq
milliequivalents
43
• Ionic solutions have a _____ in the number of positive and negative charges present because the dissolving ionic compounds have no net charge.
balance
44
How do you express the concentration of electrolytes?
45
What is dilution?
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
* Preparation of a desired solution by adding water to a concentrate.
* Moles of ____ remains the same.
solute
47
Preparation of a dilute solution from a stock solution. (3)
48
1. Mass percent =
Mass % of A = mass of A in solution / total mass of solution x 100
49
How else can you express concentration?
50
What is a mole fraction?
XA+ moles of A/ total moles of all components
51
• 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.
units.
1
liquid
52
What is molality?
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
What is Osmolality?
* 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
Urine osmolality can vary in a healthy person from __-____ mOsm/kg H2O
80 -1200
55
The most important osmols in the urine are cations___,___,___ with their corresponding anions as well as urea and glucose.
It is measured by an ______.
Na+ , K+ ,NH4+
| osmometer
56
* 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:
57
* 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.
280-290
58
What is measured osmolality higher than?
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
The difference between the measured and calculated
osmolality is termed the osmolar ___
– The osmolar ___ is normally <10mosm/L
gap
| gap
60
If we know the density of the solution, we can calculate the molality from the ____, and vice versa.
molarity
61
What do changes in colligative properties depend on?
• Changes in colligative properties depend only on the number of solute particles present, not on the identity of the solute particles.
62
Among colligative properties are: (4)
– vapour-pressure lowering
– Boiling-point elevation
– Melting-point depression
– Osmotic pressure
63
How is vapour pressure affected?
64
Why is the vapour pressure of a solution lower than that of a pure solvent? (3)
> 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
What is Raoult’s Law?
Quantifies the extent to which non-volatile solute lowers the vapour pressure of the solvent.
66
What is the formula for Raoult's law?
Note: This is one of those times when you want to make sure you have the vapour pressure of the
solvent.
67
Ideal solution:
Ideal solution: one that obeys Raoult’slaw.
68
When does Raoult's Law break down?
• Raoult’s law breaks down when the solvent-solvent and solute-solute intermolecular forces are greater than solute-solvent intermolecular forces.
69
What is Raoult's law for two components that are volatile?
• The component that is more volatile will have higher partial pressure.
70
> Non-volatile solute-solvent interactions also cause solutions to have _____ boiling points and _____ freezing points than the pure solvent.
higher
| lower
71
Goal: interpret the phase diagram for a solution.
Non-volatile solute lowers the ____ ____. Therefore the triple point - critical point curve is lowered.
vapour pressure
72
• The change in boiling point is proportional to the molality of the solution:
where Kb is the molal boiling-point elevation constant, a property of the solvent, m is the molality; ΔTb change in bpt
73
ΔTb is added to the normal boiling point of the solvent. Tb = ________
Tb = normal boiling point + ΔTb
74
At 1 atm (normal boiling point of pure liquid) there is no _____ by definition.
depression
75
What happens when a solution freezes? (2)
• 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
The melting-point (freezing-point) curve is a _____ line from the triple point.
vertical
77
• The solution freezes at a lower temperature (ΔTf) than the ___ solvent.
pure
78
_______ in freezing point (ΔTf) is directly proportional to molality (Kf is the molal freezing-point-depression constant)
Decrease
79
• The change in freezing point can be found similarly:
• Here Kf is the molal freezing-point depression constant of the solvent.
△Tf is subtracted from the normal freezing point of the solvent.
80
Note that in both equations, △T does not depend on what the solute is, but only on how many particles are dissolved.
Tb =
Tf =
```
Tb = normal boiling point + ΔTb
Tf = normal freezing point –ΔTf
```
81
* 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.
semipermeable
82
What happens in osmosis?
> 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
The pressure required to stop osmosis is known as osmotic pressure, π, calculated as follows:
84
If the osmotic pressure is the same on both sides of a membrane (i.e., the concentrations are the same), the solutions are _____.
isotonic
85
* 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.
hypertonic
crenation
hypotonic
hemolysis
86
What is Osmolarity?
• 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
What is Osmolality?
• 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
We can use the effects of a _____ property such as osmotic pressure to determine the molar mass of a
compound.
colligative
89
The van’t Hoff factor (i) is defined as the ratio of solute particles in solution to the number of formula units dissolved:
