Exam 2

Question 1

Standard state

Answer 1

a reference point used to calculate a substance’s properties under different conditions

1 M
1 atm

Question 2

example of a compound in its standard state

Answer 2

CO2 is a gas in the standard state

Question 3

Why do reactions proceed to a lower energy state when they reach equilibrium? (mathematically)

Answer 3

G = -RTln(K)

K=1 at equilibrium, so G will equal 0

Question 4

Why do reactions proceed to a lower energy state when they reach equilibrium? (conceptually)

Answer 4

as a reaction approaches equilibrium Q=K

when Q=K, ln(Q/K)=0 and therefore G=0

*this is still very mathematical

Question 5

G when Q

Answer 5

reaction has more reactants, needs to shift right towards the products, so G is negative

Question 6

G when Q>K

Answer 6

reaction has more products, needs to shift left towards the reactants, so G is positive

Question 7

G when Q=K

Answer 7

system is equilibrium, so G is 0

Question 8

G when K>1

Answer 8

G is negative

equilibrium is a state where there are more products than reactants, so the reaction proceeds right

Question 9

Graph when K>1

Answer 9

equilibrium is closer to products

Question 10

Graph when K<1

Answer 10

equilibrium is closer to reactants

Question 11

G when K<1

Answer 11

G is positive

equilibrium is a state where there are more reactants than products, so the reaction proceeds left

Question 12

difference between ΔG° and ΔG

Answer 12

ΔG° is always the same for a reaction since it is standard conditions and only changes with K. K is a set number at equilibrium.

ΔG differs for a reaction since it is related to ln(Q/K) and Q changes. ΔG is the only one that changes as a reaction proceeds and Q changes.

Question 13

axial hydrogens are _____ to one another

Answer 13

anti

Question 14

equatorial hydrogens are _____ to one another

Answer 14

gauche

Question 15

gauche

Answer 15

60 degrees

Question 16

after a ring flip, what position does an equatorial constituent have?

Answer 16

axial

Question 17

after a ring flip, what position does a pointing down consitutent have?

Answer 17

pointing down

Question 18

which way do constituents “move” positions when going from right to left in ring flip?

Answer 18

clockwise

Question 19

which way do consitiuents “move” positions when going from left to right in ring flip?

Answer 19

counter-clockwise

Question 20

steric strain

Answer 20

the van der Waals repulsion between a substituent and nearby hydrogens

Question 21

why is the equatorial position favored in cyclohexanes?

Answer 21

to minimize the steric strain

Question 22

why is the equatorial position more favored when the size of the constituents increases?

Answer 22

as the steric bulk of the constituents increases, the steric strain also increases, so want to minimize this

Question 23

relationship between ΔG and A-value

Answer 23

ΔG can be called an A-value when talking about the equatorial vs. axial position

makes sense that as K increases and there are more axial conformations, ΔG becomes more negative and more stable, which means that A-value points to more axial products

^all adds up

Question 24

A-values

Answer 24

indicate how much the equatorial position is favored over the axial position

Question 25

Relationship between ΔG and stability

Answer 25

the more negative ΔG is the more stable it is because it has lower free energy

Question 26

Bronsted-Lowry acid

Answer 26

a substance that can donate a proton (H+)

Question 27

Bronsted-Lowry base

Answer 27

a substance that can accept a proton

Question 28

amphoteric

Answer 28

water’s ability to act as an acid or a base

Question 29

autoionization of water

Answer 29

ionize H2O to give off H+ and OH- ions

Question 30

equilibrium constant of the autoionization of water (Kw)

Answer 30

1.0 * 10-14

Kw = [H3O+] [OH-]

*when H3O+ > OH- solution is acidic, and vice-versa

Question 31

Lewis acid

Answer 31

a compound that accepts an electron pair

Question 32

Lewis base

Answer 32

a compound that donates an electron pair

Question 33

Arrhenius acid

Answer 33

specifically dissociates into H+ ions in water

Question 34

Arrhenius base

Answer 34

specifically dissociates into OH- ions in water

Question 35

What do curved arrows represent?

Answer 35

collisions of molecules that lead to chemical reactions

Question 36

Where do curved arrows always start?

Answer 36

the Lewis base (electron source)

Question 37

Why are Lewis bases known as nucleophiles?

Answer 37

their negatively charged lone pairs are attracted to the positive nucleus of other atoms

Question 38

Why are Lewis acids known as electrophiles?

Answer 38

their partially positive atoms are attracted to electrons

Question 39

Carbocation

Answer 39

carbon with a formal + charge

often a Lewis acid since positive charge is attracted to electrons

Question 40

Acetic acid formula

Answer 40

CH3COOH

*weak acid

Question 41

What do we mean by stable?

Answer 41

lower in free energy

Question 42

What does the “p” indicate in like pH?

Answer 42

indicates the -log of whatever follows it

for example, pOH = -log (OH)

Question 43

strong electrolyte

Answer 43

a combined name for strong bases and acids

there is no equilibrium here. reaction goes to completion

Question 44

inductive affect

Answer 44

ability for electronegative atoms to removed electron density from the other negatively charged constituents through SIGMA bonds

can make a conjugate base more stable

Question 45

why do stronger acids have a higher K?

Answer 45

they have more stable conjugate bases (weaker) so the reaction wants to go towards the products

in addition, more stable conjugate bases means that enthalpy goes down, so G is most likely negative as well and the reaction will proceed right

Question 46

what does a lower pKa indicate?

Answer 46

a stronger acid

there is a greater concentration of H+ ions

Question 47

when is it appropriate to make the size argument when looking at conjugate bases?

Answer 47

if comparing two elements that are actually carrying the negative charge

ex: O- vs. S-

Question 48

polarizability

Answer 48

the ability to form instant dipoles

Question 49

relationship between polarizability and size

Answer 49

larger molecules are generally more polarizable than smaller molecules

Question 50

when can you not use the polarizability argument even when looking at elements carrying the negative charge?

Answer 50

if the elements are in the same row of the periodic table

there is not a big enough size difference

need to be in different rows with different orbitals

Question 51

what should you look at when you are examining the elements carrying the negative charge but they are in the same row?

Answer 51

electronegativity

Question 52

do strong acids have a Ka or pKa?

Answer 52

no

there is no equilibrium, so they have no Ka

Question 53

where does the inductive effect occur?

Answer 53

sigma bonds with two electronegative species sharing electron density

Question 54

where does resonance occur?

Answer 54

pi-bonds

move electrons through the double bonds