Chem 1B Midterm 2

Question 1

miscible

Answer 1

two liquids able to mix in any proportion into one phase —> solution

Question 2

immiscible

Answer 2

when two liquids are mixed and two layers form
eg. oil and water

Question 3

dissolution

Answer 3

the act of dissolving

Question 4

What happens to disorder when a solute is dissolved into a solvent?

Answer 4

the disorder increases

Question 5

What are the three energies of interaction? And what happens if they are all =?

Answer 5

solute: solute
solute:solvent
solvent:solvent
All equal? —> dissolve b/c entropy with increase (S>0)

Question 6

“like dissolves like”

Answer 6

solutes that can form H-bonds are quite soluble in H20
eg. ethanol, methanol, or ethylene glycol are miscible in water b/c they can form H-bonds

Question 7

Define saturated.

Answer 7

at a certain temperature, no more solute can be added

Question 8

What does the notation “A+B” mean in a phase diagram?

Answer 8

Two phases

Question 9

Solids require … to break apart.

Answer 9

energy

Question 10

When dissolving solids (salts) what returns the energy to allow the reaction to be favorable?

Answer 10

strong ion-dipole forces between solute and solvent

Question 11

If the solution gets cold after dissolving what is happening?

Answer 11

Endothermic: energy required to break the bond > energy release by interaction
(so energy is absorbed from surroundings T down)

Question 12

If the solution get hot after dissolving what is happening?

Answer 12

Exothermic: energy to break the bond < energy released from ion-dipole interaction

Question 13

… decreases gases solubility. Why?

Answer 13

Heat
b/c gases are more disordered, so solubility is unflavored by heating up the solvent

Question 14

… increases gases solubility. Why?

Answer 14

Pressure
forces more gas into the liquid

Question 15

What two things does gas solubility rely on?

Answer 15

Temperature + Pressure

Question 16

What is Henry’s Law?

Answer 16

S(gas) = K(h) * P(gas)
solubility of a gas (M: mole/kg) = Henry’s law constant (M/atm)* Pressure of gas (atm)

Question 17

Solubility of gases is ____ ____ to pressure until ___ ____ pressure.

Answer 17

linearly proportional, very high

Question 18

Define colligative properties.

Answer 18

depend on the number of solute particles, but not the kind

Question 19

If you add solute particles to a liquid what happens to VP? BP? MP? Why?

Answer 19

Vapor pressure DECREASES
BP INCREASES
-b/c solutes molecules block solvent from being able to evaporate

MP DECREASES
-b/c solvent molecules are farther away, need more E to bring back to solid state

Question 20

Gibbs Free Energy equation

Answer 20

Δ G= Δ H — T Δ S

G= free energy
H= enthalpy
T= temp
S= entropy (slope= -S)

Question 21

Whichever VP is ___ disappears.

Answer 21

higher

Question 22

Non volatile (__) solutes ___ the vapor pressure.

Answer 22

(not easily evaporated) LOWER

Question 23

Raoult’s Law

Answer 23

For ideal solutions!
P= (Xa* P°a + XbP°b)
Total Pressure (atm) = (mole fraction of solute Ppartial solute (atm) + mole fraction of solvent * Ppartial of solvent (atm))

Question 24

BP elevation

Answer 24

ΔTb= Kb*m(solute)

ΔT= change in temp. (same for °C and K)
Kb= constant
m= molality of solute (mole solute/kg solvent)

**New BP add to existing BP

Question 25

Freezing Depression

Answer 25

ΔTb= Kf*m ΔT= change in temp. (°C=K) Kf= ebullioscopic constant m= molal (moles solute/kg solvent) **For NEW MP subtract from OG

Question 26

% of a molecule in total VP

Answer 26

Ya= Pa/Ptotal= Pa/Pa+Pb= XaPa,pure/ (XaPa,pure+ Xb,Pb,pure)

Question 27

Ideal Gas Law: Increasing Pressure—> __ Temp

Answer 27

Increases

Question 28

Ideal Gas Law: Increasing Volume —> __ Temp

Answer 28

Increases

Question 29

Molecular Solids

Answer 29

made of molecules, held together by H-bonds or dipole-dipole—> lower melting points

Question 30

Network Solids

Answer 30

made of covalent bonds—> High IMF—> high melting points

Question 31

ionic solids

Answer 31

ionic bonds—> high IMF—> highest melting point

Question 32

Crystals DO /DO NOT conduct electricity

Answer 32

DO NOT CONDUCT

Question 33

1st Law of Thermodynamics

Answer 33

Energy is conserved

Question 34

2nd Law of Thermodynamics

Answer 34

Entropy (chaos) of the universe is always increasing ΔS>0

Question 35

List the thermodynamic state functions

Answer 35

only depends on current state, not how they arose Internal Energy (E/U) Free Energy (G) (spontaneous or not) Entropy (S) J/K Enthalpy (H) ΔT

Question 36

Fractional Distillation

Answer 36

“boiling off”

Question 37

Bubble point

Answer 37

temperature at which the mixture first boils during fractional distillation

Question 38

Dew point

Answer 38

Temperature at which the mixture first condenses during fractional distillation

Question 39

What happens to dew point and bubble point in pure mixtures/solutions?

Answer 39

Dew point and bubble point are equal.

Question 40

Path functions

Answer 40

heat (q) and work (w)