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Chem > AP Chem - Chapter 11 - Solutions > Flashcards

AP Chem - Chapter 11 - Solutions Flashcards

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1
Q

What is a solution

A

a homogenous mixture

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2
Q

what is the difference between a solvent and a solute

A

a solvent does the dissolving, a solute gets dissolved

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3
Q

what are the different ways to find concentration

A 
molarity
mass percent
volume percent
mole fraction
molality
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4
Q

what is the equation for molarity (M)

A

moles solute/liters solution

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5
Q

what is the equation for mass percent (%m/m)

A

mass solute/mass solution x 100

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6
Q

what is the equation for volume percent (%v/v)

A

volume solute/volume solution x 100

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7
Q

what is the equation for mole fraction (weird x)

A

moles solute/total moles

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8
Q

what is the equation for molality (m)

A

moles solute/kg solvent

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9
Q

what is the difference between molarity and molality

A

molarity changes slightly with temperature, molality doesn’t

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10
Q

what is the general rule of thumb with solubility

A

like dissolves like

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11
Q

how do you determine the polarity of a molecule

A

structure

electronegativity and bond polarity

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12
Q

what are the three steps in solution formation

A

breaking up the solute
breaking up the solvent (overcoming intermolecular forces)
allowing the solute and solvent to interact and mix

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13
Q

is breaking up the solute (step 1) endo or exothermic

A

endothermic

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14
Q

is breaking up the solvent (step 2) endo or exothermic

A

endothermic

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15
Q

is allowing the solute and solvent to interact and mix (step 3) endo or exothermic

A

exothermic

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16
Q

what is the heat of solution

A

the sum of the heat values for each step

heat of solution = heat step 1 + heat step 2 + heat step 3

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17
Q

what are the factors that affect solubility

A

structure
pressure
temperature

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18
Q

how does structure affect solubility

A

structure determines polarity, which determines solubility

polar will dissolve in polar, nonpolar in nonpolar

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19
Q

how does pressure affect solubility

A

pressure significantly increases the solubility of a gas

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20
Q

what is henry’s law

A

the amount of gas dissolved in a solution is directly proportional to the pressure of the gas above the solution

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21
Q

when does Henry’s law hold true

A

only when there is no chemical reaction between the solute and the solvent

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22
Q

how does temperature affect solubility

A

most solids dissolve better in warm liquids

gasses dissolve better in cold liquids

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23
Q

what is thermal pollution

A

when factories use water and then put it back put its warm so gasses can’t dissolve as well in it so living things in the pond suffocate.

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24
Q

when are the magnitude of the molarity and molality almost the same

A

in very dilute aqueous solutions

25
Q

what is a nonvolatile solute

A

one that has no tendency to escape from solution into the vapor phase

26
Q

how does the presence of a nonvolatile solute affect the vapor pressure of a solvent

A

it lowers it

27
Q

why will a nonvolatile solute lower the vapor pressure of a solvent

A

because the solvent is occupied with interacting with the solute, so less is available to evaporate

28
Q

what does the lowering of vapor pressure depend on

A

the number of solute particles present in the solution

29
Q

what is an ideal solution

A

a liquid to liquid solution that obeys Raoult’s Law

30
Q

in solutions where both solute and solvent are volatile, describe the vapor pressure if the solvent/solute have weak interactions (dissimilar IMFs)

A

vapor pressure will be higher than expected

31
Q

in solutions where both solute and solvent are volatile, describe the vapor pressure if the solvent/solute have strong interactions (similar, very strong IMFs)

A

Vapor pressure will be lower than expected

32
Q

what can we assume about the IMFs between the solute and the solvent when the energy of formation of solution is large and negative

A

the IMFs are strong

there will be a negative deviation from Raoult’s law

33
Q

what can we assume about the IMFs between the solute and the solvent when the energy of formation of solution is positive

A

IMFs are weaker than those among the molecules in the pure liquids
there will be a positive deviation from Raoult’s Law

34
Q

what are colligative properties

A

properties of a solution that depend only on the number, and not on the identity, of the solute particles

35
Q

How does the presence of a nonvolatile solute affect the freezing point of a solution

A

It depresses it (lowers it

35
Q

When does the normal boiling point of a liquid occur

A

At the temperature where the vapor pressure of a liquid equals exactly 1 atm

36
Q

How does a nonvolatile solute affect the boiling point of the solvent

A

It elevates it

37
Q

Why does the presence of a nonvolatile solute elevate the boiling point of the solvent

A

Because VP is lowered when we add a solute, so we need to add more energy (higher temperature) to get more solvent to evaporate so the VP will be equal to the atmospheric pressure and be able to boil

38
Q

Why does the presence of a non volatile solute lower the freezing point of the solvent

A

Solvent is busy interacting with the solute, so we have to remove even more energy to get the solvent to go from a liquid to a solid

39
Q

Why is putting salt on the roads not always effective in keeping them from freezing

A

Because if the outside temperature is lower than the freezing point of the resulting salt solution, ice forms anyway

40
Q

What is osmosis

A

The flow of solvent into the solution through the semipermeable membrane

41
Q

What is osmotic pressure

A

The pressure that must be applied to a solution to stop osmosis

42
Q

How does water tend to move/diffuse

A

From areas of high concentration to low concentration

43
Q

Why is osmotic pressure particularly useful?

A

Because a small concentration of solute produces a relatively large osmotic pressure

44
Q

What are isotonic solutions

A

Solutions that have identical osmotic pressures

45
Q

When does reverse osmosis occur

A

If a solution in contact with pure solvent across a semipermeable membrane is subjected to an external pressure larger than its osmotic pressure

46
Q

What does reverse osmosis cause

A

A net flow of solvent from the solution to the solvent

47
Q

What does the semipermeable membrane act as in reverse osmosis

A

A “molecular filter” to remove solute particles

48
Q

What does the van’t Hoff factor (little i thing) account for

A

The fact that ionic compounds ionize and produce more particles in solution

49
Q

How can you find the expected value for i

A

By noting the number or ions per formula unit (i.e. NaCl would be 2, K2SO4 would be 3, etc)

50
Q

Is the expected value of the van’t Hoff factor always what actually happens?

A

No

51
Q

Why is the expected value for the van’t Hoff factor not always true

A

Ion pairing

52
Q

What is ion pairing

A

When dissolved ions in a solution find each other swimming around and hang out for a bit and thus count as a single particle

53
Q

Why do higher concentrations of solute lead to a lower value of the van’t Hoff factor

A

There’s more of a chance for ion pairing because there is a higher concentration of ions

54
Q

A salt solution sits in an open beaker. Assuming constant temperature and pressure, the vapor pressure of the solution…

A

Decreases over time

55
Q

When is ideal behavior for a solution often observed

A

When the solute-solute, solvent-solvent, and solute-solvent reactions are very similar

56
Q

2 liquids from a solution and release a quantity of heat. How does the pressure above the solution compare to that predicted by raoult’s law?

A

It will be less

57
Q

Why will a nonpolar solute and a highly polar solvent not produce a solution (mix)

A

Because a large amount of energy would have to be expended

Chem (20 decks)

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