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MCAT Chem > Chem #9 > Flashcards

Chem #9 Flashcards

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1
Q

solutions

A

homogenous mixtures of two or more substances that combine to form a single phase, usually the liquid phase.

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2
Q

solute

A

dissolved in the solvent

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3
Q

solvent

A

: the component of the solution that remains in the same phase upon mixing.
 If both in the same phase then the one in greater amounts is the solvent.
 If same amounts, then the one that is usually the solvent is the solvent.

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4
Q

mixtures

A

such as of two gases, do not interact chemically.

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5
Q

solvation (dissolution)

A

the electrostatic interaction between solute and solvent molecules.

o Hydration: when water is the solvent.
o Break intermolecular attractions between solute and solvent molecules respectively and form new ones with each other.
o When the new interactions are stronger than the original ones, solvation is exothermic.
 Favored at low temperatures
 The dissolution of gases into liquids.
o When the new interactions are weaker than the original ones, solvation is endothermic.
 Favored at high temperatures

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6
Q

solvation is an ____ interaction

A

electrostatic

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7
Q

when new interactions after solvation are stronger than the original ones it is a ______ reaction

A

exothermic

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8
Q

when new interactions after solvation are weaker than the original ones it is a ______ reaction

A

endothermic

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9
Q

ideal solution

A

: the enthalpy of dissolution is close to zero as the overall strength of the new reactions is approximately equal to the strength of the original reactions.

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10
Q

entropy

A

measure of the number of energy microstates available to the system at a given temperature.
 OR: the amount of energy dispersed throughout a system.

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11
Q

NaCl dissolution in water and entropy

A

 Ex: NaCl in water: NaCl entropy increases as the lattice ionic bonds are broken and it forms ion-dipole interactions with water. Water is more ordered interacting with the NaCl so its entropy decrease but overall the entropy change of NaCl wins out.

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12
Q

true or false: All solutions are considered mixtures, but not all mixtures are considered solutions.

A

true

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13
Q

mOsm

A

milliosmolarity

multiply bvy 10^-3 to get osmolarity

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14
Q

solubility

A

the maximum amount of that substance that can be dissolved in a particular solvent at a given temperature.

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15
Q

saturated

A

when the maximum amount of solute has been added, the dissolved solute is in equilibrium with its undissolved state.
 If more solute is added after this point it won’t dissolve.
 Precipitating: remain in solid form.

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16
Q

precipitating

A

remain in solid form.

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17
Q

dilute

A

a solution in which the proportion of solute to solvent is small.

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18
Q

concentrated

A

a solution in which the proportion of solute to solvent is larger

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19
Q

sparingly soluble salts

A

those solutes that dissolve minimally (molar solubility <0.1 M

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20
Q

aqueous solutions

A

most common type of solution, in which the solvent is water.
o In acids, the formation of the hydronium ion can occur (H3O+).
 A H+ is never really found in solution alone so it forms a coordinate covalent bond with H2O.

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21
Q

hydronium ion

A

H3O+

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22
Q

describe the solubility of solids and gases with respect to temperature

A

Solubility of solids can be increased by adding temperature.
Solubility of gases can be increased by decreasing temperature.

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23
Q

complex ion

A

(coordination compound): refers to a molecule in which a cation is bonded to at least one electron pair donor (which could include the water molecule)
 Ligands: the electron pair donor
 Complexation reaction

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24
Q

ligands

A

the electron pair donor

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25
Q

what do complex ions and transition metals do in biology?

A

Complex ion binding and transition metal complexes help macromolecules such as proteins carry out their functions: Iron cation in hemoglobin.

The presence of a transition metal allows coenzymes and cofactors to bind other ligands or assist with electron transfer.

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26
Q

_____ is the opposite of the common ion effect

A

Formation of complex ions increases the solubility of otherwise insoluble ions (the opposite of the common ion effect)

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27
Q

coordinate covalent bonds

A

hold the complexes together, in which an electron pair donor and an electron pair acceptor form very stable lewis acid-base adducts.

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28
Q

chelation

A

in some complexes, the central cation can be bonded to the same ligand in multiple places.
 The organic molecules are usually large and have the ability to double back.

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29
Q

what are the ways concentration can be measured of a solution?

A

percent composition by mass
mole fraction
molarity
molality

30
Q

dilution

A

a solution is diluted when solvent is added to a solution of higher concentration to produce a solution of lower concentration.

31
Q

for solutions, equilibrium is defined as the ____

A

saturation point

32
Q

what happens once the saturation point has been reached in a reaction and more solute is added?

A

o Once some solute is dissolved, the reverse process of precipitation of the solute will also begin.

33
Q

saturation point

A

the point at which the rates of dissolution and precipitation are equal.
o The concentration of the dissolved solute reaches a steady-state (constant value)
o Delta G is 0 at this point.

34
Q

facts about the solubility product constant

A

Pure solids and liquids do not appear in the equilibrium constant.
These should NEVER have denominators.

35
Q

solubility product constant

A

the equilibrium constant for an ionic compound’s solubility in aqueous solution.
 Concentrations are equilibrium concentrations.
 Increase T: increases it for non-gas and decreases for gas

36
Q

ion product

A

 Used to determine where the system is with respect to equilibrium.
 Uses concentrations at the given moment.
 IPKsp: supersaturated
• Able to do when a solution is heated, dissolution occurs, and then the solution is cooled.
 IP = Ksp: equilibrium, saturated

37
Q

molar solubility

A

for a substance it is the molarity of a solute in a saturated solution.
 “x” in the equations, the thing that is dissolving for sure.
 The compound’s concentration (in moles/liter) at equilibrium at a given temperature.

38
Q

complex ions

A

The formation of a complex increases the solubility of other salts containing the same ions because it uses up the products of those dissolution reactions, shifting the equilibrium, to the right (opposite of the common ion effect)

 The formation of complex ions increases the solubility of salt in solution.
 Have very high Ksp. Very stable molecules due to dipole-dipole interactions.
 The Ksp of the solution is Ksp, but the formation of the complex ion in solution is termed Kf (formation or stability constant).
 The dissolution of the metal ion is the rate limiting step.
 The large Kf of the second reaction can drive a reaction with a smaller Ksp value.

39
Q

the formation of a complex ion ______ the solubility of salt in solution

A

increases

40
Q

common ion effect

A

the reduction in molar solubility of a salt when it is dissolved in a solution that already contains one of its constituent ions.

41
Q

high vapor pressure means ___

A

Molecules that evaporate very easily have a high vapor pressure.

42
Q

colligative properties

A

: physical properties of solutions that are dependent on the concentration of dissolved particles but not on the chemical identity of the dissolved particles.

43
Q

Mixtures that have higher vapor pressure than predicted by Raoult’s law have _________ Therefore they want to evaporate quicker.

A

stronger solvent-solvent and solute-solute interactions than solvent-solute interactions. Therefore they want to evaporate quicker.

44
Q

raolt’s law

A

accounts for vapor pressure depression caused by solutes in solution.
o As solute is added to a solvent, the vapor pressure of the solvent decreases proportionately.
o The presence of the solute molecules can block the evaporation of solvent molecules but not their condensation.
o Holds only when the attraction between the molecules of the different components of the mixture is equal to the attraction between the molecules of any one component in its pure state.

45
Q

boiling point elevation

A

when a nonvolatile solute is dissolved into a solvent to create a solution, the boiling point of the solution will be greater than that of the pure solvent.
o Boiling point: the temperature at which the vapor pressure of the liquid equals the ambient (incident) pressure.
o This is due to a lower vapor pressure caused by the solute.
o van’t Hoff factor: corresponds to the number of particles into which a compound dissociates in solution.
 Ex: NaCl: 2
 Ex: glucose: 1, because glucose does not readily dissociate in water.

46
Q

freezing point depression

A

lower freezing point at a result of the presence of solutes.
o The presence of solute particles in a solution interferes with the formation of the lattice arrangement of solvent molecules associated with the solid state.
 A greater amount of energy must be removed from the solution to get it to solidify.
o Reason why we salt roads during storms to prevent more freezing of water.

47
Q

osmotic pressure

A

o A sucking pressure generated by solutions in which water is drawn into a solution.
o Formally, osmotic pressure is the amount of pressure that must be applied to counteract this attraction of water molecules for the solution.

48
Q

Can solids be dissolved in other solids?

A

Yes, metal alloys.

49
Q

The ____ is the component of the solution that remains in the same phase after mixing. If the two substances are already in the same phase, then the ____ is the component present in greater quantity.

A

solvent

solvent

50
Q

determining the spontaneity of dissolution requires analyzing the ___ and the ____ of the process

A

enthalpy and entropy

51
Q

when the change in Gibbs free energy for the dissolution is positive, the process will be _______ and the solute is said to be ____

A

nonspontaneous

insoluble

52
Q

saturation occurs at a specific concentration at a specific ____

A

temperature

53
Q

solubility of solids can be increased by increasing _____. Solubility of gases can be increased by ____ or increasing the ______ of the gas above the solvent.

A

temperature

decreasing temperature, partial pressure

54
Q

Normality is ____ if a compound does not dissociate

A

1

55
Q

to calculate molarity, the ____ volume of the solution must be known

A

final/total

56
Q

the equilibrium position is ________

A

the lowest energy state of a system under a given set of temperature and pressure conditions.

57
Q

solubility product constants, like all other equilibrium constants, are _____ dependent

A

temperature

58
Q

How is the solubility product effected by changing temperature for solids and gases, respectively?

A

For solids, increasing temperature increases Ksp.

For gases, decreasing temperature increases Ksp.

59
Q

For solutions, a solution at equilibrium is called _____

A

saturated

60
Q

On a molecular level, the presence of the solute molecules can _______, leading to a decrease in vapor pressure

A

block the evaporation of solvent molecules but not their condensation.

61
Q

Raoult’s law only holds when _____.

A

the attraction between the molecules of the different components of the mixture is equal to the attraction between the molecules of any one component in its pure state.

62
Q

when you have to compounds that exert vapor pressure in a mixture then the total vapor pressure is equal to the _____

A

addition of the vapor pressures of the two components.

63
Q

why does boiling point elevation occur?

A

the presence of a solute lowers the vapor pressure of a solution and thus it will require more energy or a greater temperature for the vapor pressure to equal the ambient pressure and boiling to occur

64
Q

why does freezing point depression occur?

A

the presence of solute particles interferes with the formation of a lattice arrangement in the solid state.

65
Q

difference in final answer for boiling point elevation and freezing point depression?

A

temperature is rising by whatever the change is while freezing point is decreasing by whatever the change is.

66
Q

For water, molarity and molality are very similar at room temperature because _____

A

water has a density of 1 g/ml

67
Q

name the colligative properties of solutions

A

vapor pressure depression, boiling point elevation, freezing point depression, osmotic pressure

68
Q

solutions are _____ mixtures

A

homogenous

69
Q

when calculating the mass percent, it is important to consider what for the denominator?

A

the mass of the solution is equal to the mass of the solvent + the mass of the solute.

70
Q

mixtures that have higher vapor pressure than predicted by Raoult’s law have ____.

A

stronger solvent-solvent and solute-solute interactions than solvent-solute interactions

MCAT Chem (12 decks)

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