EXAM 3

Question 1

What is the Reaction Quotient (Q)?

Answer 1

The ratio of [products] to [reactants] at any given time in the reaction

Question 2

What is the relationship between Q and K at equilibrium?

Answer 2

At equilibrium, Q = K

Question 3

What does it indicate when Q < K?

Answer 3

Reaction moves in forward direction to reach equilibrium

Question 4

What does it indicate when Q > K?

Answer 4

Reaction moves in reverse direction to reach equilibrium

Question 5

What do ICE Tables showcase?

Answer 5

How the initial concentrations change to reach equilibrium concentrations and can also be used to determine K

Question 6

What is the general form of a reaction in an ICE Table?

Answer 6

aA + bB ⇌ cC + dD

Question 7

In an ICE Table, what does ‘I’ stand for?

Answer 7

Initial concentrations

Question 8

In an ICE Table, what does ‘C’ stand for?

Answer 8

Change in concentrations

Question 9

In an ICE Table, what does ‘E’ stand for?

Answer 9

Equilibrium concentrations

Question 10

What is the formula to calculate K using ICE Table values?

Answer 10

K = [Ic + cx]c[Id + dx]d / [Ia - ax]a[Ib - bx]b

Question 11

How does Le Chatelier’s Principle relate to Q and K?

Answer 11

If Q > K, negative change of products, positive change of reactants; if Q < K, positive change of products

Question 12

What happens to the reaction if the concentration of a product is increased?

Answer 12

Q > K → shift in reverse direction to form reactants until Q = K

Question 13

What happens if the concentration of a reactant is increased?

Answer 13

Q < K → shift in forward direction to form products until Q = K

Question 14

How does temperature affect an endothermic reaction?

Answer 14

Increase temperature → Q < K → shift in forward direction; Decrease temperature → Q > K → shift in reverse direction

Question 15

How does temperature affect an exothermic reaction?

Answer 15

Add heat → Q > K → shift in reverse direction; Remove heat → Q < K → shift in forward direction

Question 16

What is the effect of increasing pressure on a gas reaction?

Answer 16

Favor side with less moles of gas

Question 17

What is the equation that relates ΔG to Q?

Answer 17

ΔG = ΔG° - RTlnQ

Question 18

What is the relationship between ΔG° and K at equilibrium?

Answer 18

ΔG° = -RTlnK

Question 19

What does Q < K imply about spontaneity?

Answer 19

ΔG < 0 → spontaneous in forward direction

Question 20

What does Q > K imply about spontaneity?

Answer 20

ΔG > 0 → spontaneous in reverse direction

Question 21

What does K > 1 indicate about ΔG°?

Answer 21

ΔG° < 0 → product favored at equilibrium

Question 22

What does K < 1 indicate about ΔG°?

Answer 22

ΔG° > 0 → reactant favored at equilibrium

Question 23

What defines strong acids?

Answer 23

Strong acids donate protons and undergo 100% ionization

Question 24

What defines weak acids?

Answer 24

Weak acids have [HA]INITIAL > [H3O+]eq

Question 25

What is Ka?

Answer 25

The ratio of equilibrium concentration of H3O+ and A- to HA

Question 26

What does a higher Ka indicate?

Answer 26

Stronger acid

Question 27

What does a higher pKa indicate?

Answer 27

Weaker acid

Question 28

What defines strong bases?

Answer 28

Strong bases accept protons and undergo 100% ionization

Question 29

What defines weak bases?

Answer 29

Weak bases have [B]INITIAL > [OH-]eq

Question 30

What is the amphiprotic nature of water?

Answer 30

Water can act as an acid or a base

Question 31

What factors affect acid strength?

Answer 31

Bond strength, bond polarity, inductive effect, resonance

Question 32

What is the Common Ion Effect?

Answer 32

Presence of a common ion suppresses ionization of a salt compared to pure water

Question 33

What is the purpose of buffers?

Answer 33

Buffers minimize changes in pH

Question 34

What components do buffers typically contain?

Answer 34

Weak acid/base and conjugate base/acid in substantial amounts

Question 35

What happens when H3O+ is added to a buffer?

Answer 35

Equilibrium shifts left; H3O+ reacts with conjugate base to produce weak acid

Question 36

What happens when OH- is added to a buffer?

Answer 36

OH- reacts with weak acid to produce more conjugate base

Question 37

What is the Henderson-Hasselbalch equation used for?

Answer 37

To calculate pH of buffer solutions

Question 38

What does pH > pKa indicate?

Answer 38

[A-] > [HA]

Question 39

What does pH < pKa indicate?

Answer 39

[HA] > [A-]

Question 40

What is the initial region in a strong acid and strong base titration?

Answer 40

Strong Acid Present

Question 41

What occurs at the equivalence point in a strong acid and strong base titration?

Answer 41

Moles of OH- = moles of H3O+ → salt formed

Question 42

What is the half-equivalence point in a weak acid and strong base titration?

Answer 42

[HA] = [A-], pH = pKa

Question 43

What is the excess base scenario in a weak acid and strong base titration?

Answer 43

Use BCA and [OH-] to calculate pH

Question 44

What is the half-equivalence point in a strong acid and weak base titration?

Answer 44

[B] = [HB], half of moles of B converted to HB

Question 45

What is the excess acid scenario in a strong acid and weak base titration?

Answer 45

Use BCA and [H3O+] to find pH

Question 47

What factor affects the strength of an acid?

Answer 47

The relative stability of the conjugate base ## Footnote The strength of an acid is determined by how well it ionizes.

Question 48

How does bond strength influence acid strength?

Answer 48

For H-X in the same group, larger partner atoms allow for greater dispersion of electron density, leading to stronger acids ## Footnote Larger surface areas help stabilize the conjugate base.

Question 49

What is the relationship between bond polarity and acid strength?

Answer 49

In H-X of the same period, greater electronegativity of the partner atom leads to better dispersion of electron density, making the acid stronger ## Footnote A higher partial positive charge on H makes it easier to ionize.

Question 50

What is the inductive effect in relation to oxoacids?

Answer 50

Greater electronegativity of X in H-O-X pulls electron density from O-H, making it easier for H to ionize ## Footnote This effect is amplified with more oxygen atoms.

Question 51

How does resonance affect acid strength?

Answer 51

More resonance in the conjugate base with minimal formal charges leads to greater stability and stronger acids ## Footnote Stability of the conjugate base is key to acid strength.