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Chemistry > Solutions, solubility, colligative, properties and colloids > Flashcards

Solutions, solubility, colligative, properties and colloids Flashcards

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1
Q

What is a solution

A

Homogeneous mixture of two or more pure substances

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2
Q

What is a solvent

A

The liquid in which the solid liquid or gas is dissolved

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3
Q

what is a solute

A

the substance that is dissolved in the solvent

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4
Q

What is saturated solution?

A

A solution in which no more solute will dissolve

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5
Q

Give an example for 3 different types of solutions, they’re solute, solvent.

A
  1. Gaseous solutions - solute is Gas, liquid, solid, - solvent is gas,

an example is Air, Chloroform in N2, Camphor in N2.

  1. Liquid solutions - solute = gas, solid, liquid - Solvent = Liquid.

An example, Oxygen in blood, vodka (ethanol and water), salt in water.

  1. Solid solutions - solute = gas, liquid, solid - Solvent = solid

an example = sold Co2 in Fire extinguisher, mercury with silver (tooth filling) and silver in gold.

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6
Q

Solubility

A

Amount of solute that will dissolve in a given amount of solvent at a given temperature and pressure.

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7
Q

In regards to they intermolecular forces, how do they affect the solubility? and what are examples of these?

A

The molecular structure plays an important role, polar solvent/polar solute OR nonpolar solvent/ nonpolar solute.

Water (polar solvent) dissolves sugar (polar solute)
Water (polar solvent) does not dissolve oil (non-polar solute)
Oil (non-polar solute) dissolves in hexane (non-polar solvent)

Intermolecular forces drive solubility - solute-solvent interactions must be stronger than solute-solute interactions for a substance to dissolve

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8
Q

Is solution formation exothermic of endothermic? Explain the steps for solution formation.

A

When the solvent and solute mix together, energy change is required.

  1. The solvent and solution have to overcome intermolecular forces, this is achieved by separation of solute molecules This requires energy via heat (delta H1). Heat is then absorbed causing an endothermic reaction.
  2. The solvent is required to make space for the solute molecules, and therefore also requires a endothermic reaction by acquiring energy via heat (delta H2).
  3. The solute and solvent particles are then attracted to on another causing the formation of a solute-solvent interaction. Energy (heat delta H 3) is released through these interactions - therefore, it’s a exothermic reaction.
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9
Q

What makes molecules polar and nonpolar?

A

The uneven distribution of elections

Polar molecules are those that possess regions of positive and negative charge. Water is an example of a polar material. The type of bonds it has, when coupled with its shape, gives one end of the molecule a slight positive charge (the hydrogen end) and the other a slight negative charge (the oxygen end). These charges are attracted to the charges on other polar molecules.

Nonpolar molecules are those that do not possess regions of positive and negative charge. Ethane is an example of a nonpolar material. The type of bonds it has, when coupled with its shape, leaves the molecule with no regions of charge. Generally, the more carbon and hydrogen atoms a molecule has, the less polar (more nonpolar) it will be.

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10
Q

What makes a molecular polar in solubility?

A

The –OH group is polar and can engage in hydrogen bonding with water

Carbon chains are nonpolar and typically insoluble in water. - e longer the carbon chain gets, the more nonpolar character the molecule
exhibits

Water for example - is polar molecule. Had electronegativity (draw electrons to its side) The
- OH group is polar and engage with hydrogen bonding with water.

Carbon chains are non-polar and insoluble in water.

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11
Q

Does a polar solute dissolve in a polar solvent?

A

Yes, for example - water, because its molecules are
attracted to the polar water molecules ultimately lowering of energy (enthalpy).

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12
Q

Does nonpolar solute dissolve in nonpolar solvent?

A

Yes, because the dispersion forces are of comparable strength

  • no change in enthalpy but molecules being mixed up (dissolved) is more
    probable
  • entropy (increased probability) is the driving force here
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13
Q

Give an example of a miscible solution and immiscible solution?

A

ethanol and water - miscible

Oil and water - immiscible

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14
Q

What do Ionic solids consist of?

A

cations and anions in a repeating orderly arrangement called a crystal lattice.

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15
Q

are ionic solids charge positive, negative or neutral?

A

An ionic solid is electrically neutral – the number of positive charges must balance the number of negative charges.

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16
Q

What happens to ionic solids when dissolved in water? and are all ionic solids soluable in water?

A

Ions become aquated (surrounded by water molecules) and are no longer associated with each other.

All have a varying degree of solubility in water, Ionic compounds dissociate into their constituent ions when
dissolved in water.

dissolve in water when the ion-dipole
attractions overcome both ion-ion and dipole-dipole
attractions.

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17
Q

What is the formula for concentration?

A

C = amount of solute/volume of solution

Molar concentration (M or mol L-1) = moles of solute per litre of solution.

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18
Q

What some examples are “always soluble” ionic compounds?

A

All compounds with
ammonium or alkali metal ions
NH4+, Li+, Na+, K+, Rb+, Cs+

All compounds with the
following anions:
NO3
− and ethanoate (acetate)
CH3CO2-

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19
Q

What some examples are “mostly soluble” ionic compounds?

A

All compounds of Cl −, Br −, I −
except with Ag+, Pb2+, Hg2^2+
All compounds of SO4
2 −except with Pb2+, Ca2+, Sr2+, Ba2+, Hg2^2+

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20
Q

What some examples are “mostly insoluble” ionic compounds?

A

All compounds of PO4
3−, CO32−, S 2-except with ammonium or alkali metal ions

All compounds of OH −
except with ammonium or alkali metal ions.

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21
Q

What is a saturated solution?

A

A saturated solution is one in which no more of the solute can be dissolved, at
that temperature.

If further amounts of solid are added beyond that maximum, then a dynamic
equilibrium will exist between the solid and ions in solution, but the concentration
of ions in solution will remain at the maximum possible, but will not go beyond it.

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22
Q

What is molar solubility? and can is be used to calculate Ksp

A

Molar solubility (s) is the molar concentration of a salt that is dissolved in its saturated solution

Molar solubility of pure solutions can be used to calculate Ksp (and vice
versa) assuming that all of the salt that dissolves is 100% dissociated into
its ions

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23
Q

What is the van’t Hoff Factor?

A

The van’t Hoff factor is the ratio between the concentration of particles produced when the substance is dissolved, and the concentration of a substance as calculated from its mass, c.

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24
Q

What is the van’t Hoff factor for most non-electrolytes such as surcrose?

A

dissolved in water have a van’ t
Hoff factor of 1.

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25
Q

What is the van’t Hoff factor for ionic compounds such as Nacl dissolved in water?

A

the van’t Hoff factor
is equal to the number of ions produced upon dissolution.
* The van’t Hoff factor i = 2 for 100 % dissociation of NaCl.

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26
Q

In relation to the van’t hoffs factor, when does ion pairing occur?

A

occurs to some extent in electrolyte solutions of high concentration resulting in a lower van’t Hoff factor. Some oppositely charged ions form closely
associated pairs, which behave more like they were single molecules.

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27
Q

When given a range, how do you know which Ksp value has the least solubility?

A

The smaller the Ksp the lower the solubility

28
Q

What is a dynamic equilibrium?

A

A reversible process is said to be in dynamic equilibrium when the forward and reverse processes occur at the same rate, resulting in no observable change in the system. Once dynamic equilibrium is established, the concentrations or partial pressures of all species involved in the process remain constant.

29
Q

What is the importance of the application of the solubility product Ksp?

A

It is important in the pharmaceutical and industrial compounds, alse used in agriculture

30
Q

What does the constant ksp do?

A

It the solubility product, the dissolutions of slightly soluble ionic solids in water. Can be used to quantify solubility.

31
Q

What is molar solubility?

A

The molar concentration of a salt that is dissolved in its saturated solution

32
Q

What does molar solubility calculate?

A

Ksp - vise versa. Assuming that all of the salt that dissolves is 100% dissociated into its ions.

33
Q

How do you determine solubility?

A

If you have a saturated solution with an existing dynamic equilibrium, the crystal formed with detach particles in the water.

A known volume of the filtered saturated solution is transferred into a new beaker - water is then evaporated leaving residue of the solid compound.

Mass is then determined and weighed, where calculation of the solubility can be taken ( n = m/M) and (S=Concentration = n/V)

34
Q

Describe the common Ion effect?
and is molar solubility greater or smaller in presence of common ion?

A

States that any ionic salt is less soluble in the presence of a common ion - an ion that is a component of salt.

The addition of another salt will influence and dissociate the existing ions. Le chateliers principle predicts that the addition of a common ion will shift the equilibrium to the left and the solubility of the solid will decrease.

The molar solubility s, is ALWAYs smaller in the presence of a common ion

35
Q

What are the differences between molarity and molality?

A

Molarity - expressing the concentration of a solution (mol L-1) - the amount of substance in particular volume of solution = molar concentration.

Molarity (c) = amount of solute (mol) / Volume of solution (L)

changes as temperature changes, as solutions increase their volume when the temperature changes.

Molality - expressing solution compositions that involve colligative properties - properties are proportional to molality.

Molality (b) = amount of solute (mol)/ mass of solvent (kg)

molality is temperature independent as mass does not depend on temperature.

36
Q

What are colligative properties?

A

Solution properties that depend on solute concentrations but not their chemical nature.

Example - they have the same amount but different chemical structures.

non-volatile and non electrolytes.

arise due to attractive interactions between solute particles and solvent molecules.

37
Q

What are examples of colligative properties?

A

Vapour pressure lowering
boiling point elevation
Freezing point depression
Osmotic pressure

38
Q

Explain the relation colligative properties have in regards to liquid-vapour equilibrium, and the effects of solutes on vapour pressure?

A

When heat is applied to water for example, in a closed cavity, the rate of evaporation exceeds the rate of condensation, eventually rate of evaporation equals the rate of condensation. creating a dynamic equilibrium. The gas vapour returns to a liquid state and vice versa. This creates whats called an equilibrium vapour pressure - the pressure exerted by a vapour or gas which is in equilibrium with a liquid.

However when a solute is added into the solute, it doesn’t allow free movement of the molecules and restricts the molecules. this inhibits the kinetic energy produced, thus lowering the vapour pressure in the cavity.

39
Q

Explain how the colligative properties are impacted if solutes are added in water, and the effects on on boiling point elevation and freezing point depression

A

Boiling water - if solutes are added the boiling point increases,

Freezing point depression - if solutes are added there is a decrease in temperature (freezing point lowers)

These factors are dependent on the molality of the solution

40
Q

How do you calculate the molality?

A

m = number of mol in solute (mol) / mass of solvent (kg)

41
Q

Do all solutes have the capacity to change the boling point and freezing point?

A

no

42
Q

Describe what the van’t hoff factor is?

A

The dissociation of salts only occur in specific solutions

Sum of the number of cations

Is the ratio between the concentration of particles produced when the substance is dissolved, and the concentration of a substance as calculated from its mass, c

43
Q

What is the van’t hoff factor for ionic compound such as Nacl dissolved in water?

A

Considered to always be one - we don’t change the equations as the the van’t hoff factor is equal to the number of ions produced upon dissociation of Nacl

44
Q

What is the van’t hoff factor for non-electrolytes such as sucrose dissolved in water?

A

Have a van’t hoff factor 1

45
Q

What is the importance of van’t hoff factor?

A

Modifies the boiling point elevation and freezing point depression

46
Q

When the concentration increases in a solution, why does the the van’t hoff factor decrease?

A

In most ionic compounds dissolved in waterm the van’t hoff factor is usually equal to the number of of discrete ions in a formula units of substance, This is true for ideal solutions on, as occasionally ion pairing occurs in solution.

the ion pairing (associates together) and behaves as one particle

47
Q

What is the constant of Kfp?

A

1.85 degrees

48
Q

What is the constant of Kbp?

A

0.51 degrees

49
Q

What is Osmosis?

A
  • Osmosis is a net shift of water through a semipermeable membrane.
  • In living organisms, membranes keep mixtures and solutions organised and
    separated. Semi-permeable membranes allow substances to selectively pass
    through.
    Osmosis occurs in the direction of net movement of solvent from the more
    dilute solution (or pure solvent) into the more concentrated solution.
50
Q

What is hypotonic?

A

A solution with a lower osmotic pressure than the cell fluid is

51
Q

What is hypertonic?

A

A solution that has higher salt concentration

52
Q

What is isotonic?

A

A solution that has the same osmotic pressure as the cells is isotonic
with the cells.

53
Q

What is osmotic pressure?

A

The pressure needed to prevent any osmotic flow when one of the liquids is a
pure water is called the osmotic pressure of the solution (in Pa).

54
Q

How do you calculate osmotic pressure?

A

Osmotic pressure = icRT

R= gas constant
c = Molar concentration
i = van’t hoff factor

55
Q

Will higher or lower concentration have osmotic pressure?

A

higher concentration - is going to have higher osmotic pressure

56
Q

What happens when something dissolve in water?

A

It forms dispersion, a system of discrete particles in a continuous phase = called a colloid.

think of soil in water

57
Q

What size range is a colloid

A

1nm to 1000nm the particles (disphersed phase) are larger than the solvent molecules (continuous phase) but too small to be visable

58
Q

What distinguished a colloid from a suspension and a solution?

A

Solution (smaller, less than 1nm), colloid , suspension (biggest)

59
Q

Do the properties of colloids fully given by their chemical composition?

A

No they are not fully given by their chemical composition, Their properties depend on their physical structure (size and shape). Solutions do not depend on the physical structure of the particles)

60
Q

Are dispersed system in the thermodynamic equilibrium?

A

They are not stable (unstable)

Solutions ar estable

61
Q

What colloid types do we have?

gas dispersed in liquid =
liquid in liquid =
Solid in liquid =

A

foam = whipped cream
emulsion = mayonnaise
sol = mud

62
Q

What are lyophilic colloids?

A

when they like water = lyophilic (hydrophilic)
e(solvent attracting, solvent loving)
organic macromolecules - gelatin, starch and proteins.

The particles in a lyophilic system have a
great affinity for the solvent.
* If water is the dispersing medium, it is often known as hydrophilic colloids.
* Readily solvated (combined chemically or physically, with the solvent) and dispersed, even at
high concentrations.

63
Q

What is lyophobic?

A

(solvent repelling, solvent hating) - The particles resist solvation and dispersion in the
solvent.
- The concentration of particles is usually relatively low.
- These colloids are easily precipitated on the addition of small amounts of electrolytes, by
heating or by shaking
- Less stable as the particles surrounded only with a layer of positive or negative charge
- Examples of lyophobic sols include soils

64
Q

What is the tyndall effect?

A
  • Distinguishing some colloids from solutions can be difficult–even with a microscope.
  • One way to tell a colloid from a solution is by using the Tyndall effect, the capacity
    of colloid particles to scatter light.
  • Dissolved solutes are much smaller– too small to scatter light.
65
Q

How does coagulation occur with colloids? (stability)

A

Coagulation

particles of clay, interact with each other, form aggregates (heavier),gravity takes it toll and sinks the particles to the bottom= sedimentation

we can stabilize colloids to prevent this.

A colloidal system can be destroyed, or coagulated, by the addition of ions having a charge opposite to that of the
colloidal particles.
The added ions neutralize the charged colloidal particles. The particles can clump together to form heavier
aggregates and precipitate from the dispersion.(

66
Q

What happens to oils and water? colloids when mixed with water?

A

Forms an Emulsion

two types of emulsion depending what continuous phase you have.

Oil in water, oil is a dispersed phase and water is continuous phase (immiscible liquid - do not mix). oil droplets are dispersed in water - cream, mayo, paints etc

Water in oil, water is a dispersed phase and water is continuous phase

Chemistry (9 decks)

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