5. Solutions

Question 1

What is a solution?

Answer 1

A homogeneous mixture of solute dissolved uniformly in solvent.

Question 2

What is a solute?

Answer 2

Minor component of a solution; substance being dissolved.

Question 3

What is a solvent?

Answer 3

Major component; dissolves the solute.

Question 4

What is an aqueous solution?

Answer 4

Solution where the solvent is water.

Question 5

What is concentration?

Answer 5

Amount of solute dissolved in solvent; e.g., molarity, molality.

Question 6

What is an unsaturated solution?

Answer 6

Contains less than the maximum solute that can dissolve.

Question 7

What is a saturated solution?

Answer 7

Contains maximum solute; excess solute remains undissolved.

Question 8

What happens at dynamic equilibrium?

Answer 8

Rate of dissolution equals rate of precipitation.

Question 9

What is a supersaturated solution?

Answer 9

Contains more solute than normally possible at given temp/pressure.

Question 10

What is crystallization?

Answer 10

Dissolved solute comes out of solution as solid crystals.

Question 11

What is solubility?

Answer 11

Ability of a substance to dissolve in a solvent.

Question 12

What are the general solubility rules for salts?

Answer 12

Group 1 metal cations, NO3-, ClO4-, C2H3O2-, and NH4+ are soluble; Ag+, Pb2+, Hg2+, OH-, S2-, CO32-, PO43- are generally insoluble.

Question 13

Example: Is KBr soluble?

Answer 13

Yes, because K+ is a Group 1 metal cation.

Question 14

What are electrolytes?

Answer 14

Substances that dissociate into ions in water; conduct electricity.

Question 15

What are strong electrolytes?

Answer 15

Fully dissociate; soluble ionic compounds, strong acids & strong bases.

Question 16

What are weak electrolytes?

Answer 16

Partially dissociate; weak acids/bases.

Question 17

What are non-electrolytes?

Answer 17

Do not dissociate; e.g., glucose (C6H12O6).

Question 18

How does temperature affect solubility of solids?

Answer 18

Higher temp increases solubility.

Question 19

How does temperature affect solubility of gases?

Answer 19

Lower temp increases gas solubility.

Question 20

How does pressure affect solubility of gases?

Answer 20

Higher pressure increases gas solubility.

Question 21

What is spectrophotometry?

Answer 21

Measures light absorption by solution to determine concentration.

Question 22

What is Beer’s Law?

Answer 22

A = εℓc; Absorbance is directly proportional to path length and concentration.

ε: molar absorptivity
ℓ: path length
c: conc of solution

Question 23

What is polarity?

Answer 23

Separation of electric charge in a molecule; dipole moment.

Question 24

What is the ‘like dissolves like’ principle?

Answer 24

Polar dissolves polar; non-polar dissolves non-polar.

Question 25

What are London Dispersion Forces?

Answer 25

Weakest IMF; temporary dipoles.

Question 26

What are dipole-dipole interactions?

Answer 26

Medium IMF; attractions between polar molecules.

Question 27

What is hydrogen bonding?

Answer 27

occurs with H bound to N, O, or F.

Question 28

How is matter classified?

Answer 28

Pure substances (elements, compounds) vs. mixtures (homogenous, heterogenous).

Question 29

What is molarity (M)?

Answer 29

Moles of solute per liter of solution.

Question 30

What is molality (m)?

Answer 30

Moles of solute per kg of solvent.

Question 31

What is normality (N)?

Answer 31

Equivalents per liter of solution; for acids/bases. Normality = number of equivalents x molarity

Question 32

What is mole fraction?

Answer 32

Ratio of moles of one component to total moles in solution. Mole fraction of solute = moles of solute/ total moles in solution

Question 33

What is the dilution formula?

Answer 33

M1V1 = M2V2. M= molarity V= volume

Question 34

What are colligative properties?

Answer 34

Depend upon the concentration of solute molecules or ions, but not upon the identity of the solute itself vapor pressure lowering, boiling point elevation, freezing point depression, osmotic pressure.

Question 35

What is Raoult’s Law?

Answer 35

Vapor pressure of the solution after the solute has been added = mole fraction of the solvent x pure Vapor pressure of solvent

Question 36

What is boiling point elevation?

Answer 36

ΔTb = iKbm ΔTb = change in temperature kb = solvent’s boiling point elevation constant i = solute’s van’t Hoff factor m = molality adding solute raises boiling point.

Question 37

What is freezing point depression?

Answer 37

ΔTf = -iKfm ΔTf = change in temperature kf = solvent’s freezing point depression constant i = solute’s van’t Hoff factor m = molality adding solute lowers freezing point.

Question 38

What is osmotic pressure?

Answer 38

Π = iMRT; pressure to stop osmosis. Π = osmotic pressure (atm) i = van’t Hoff factor M = molarity (M) R = universal gas constant (0.0821L*atm*K-1*mol-1) T = temperature (K)

Question 39

What is a molecular equation?

Answer 39

Shows all compounds as molecules.

Question 40

What is an ionic equation?

Answer 40

Shows compounds as separate ions.

Question 41

What are spectator ions?

Answer 41

are ions that do not take part in the reaction, and are found in solution before and after the reaction (do not precipitate).

Question 42

What is a net ionic equation?

Answer 42

Net Ionic Equations are equations that only shows the elements, compounds, and ions that are directly involved in the reaction. It is the equation without all the spectator ions since they do not participate in the reaction. We can use the salt solubility rules described earlier in chapter 5.1 to determine which compounds can dissolve and which ones form a precipitate.

Question 43

Non-colligative properties

Answer 43

depend on the identity of the dissolved species and solvent. For example, since surface tension is a non-colligative property, it is different for water and ethanol. The difference in surface tension for these compounds is because of their different identities and properties.

Question 44

what is surface tension, adhesion, cohesion

Answer 44

Surface tension is the property of a liquid that allows it to resist an external force due to the cohesive nature of its molecules. Recall that cohesive forces are the attractive forces between molecules of the same substance, while adhesive forces are attractive forces between molecules of different substances.

Question 45

T/F, Adding non-volatile solutes to a solution decreases its vapor pressure, which in turn decreases its freezing point.

Answer 45

T

Question 46

as vapor pressure increases, boiling point ____ and vice-versa

Answer 46

decreases

Question 47

When is the vapor pressure equal to the atmospheric pressure.

Answer 47

Boiling point