19.2.6 Electrochemicamical Determinants of Equilibria

Question 1

Electrochemical Determinants of Equilibria

Answer 1

• At equilibrium, the Nernst equation reduces to E ̊ cell = (R · T) / (n · F) · lnK eq .
• This relationship can be used to calculate equilibrium constants (K eq ) based on electrochemical data.

Question 2

note

Answer 2

• At equilibrium, there is no driving force for a redox reaction to proceed in either direction, so the cell voltage (E cell ) is zero. This can be used to simplify the Nernst equation to E ̊ cell – (R · T) / (n · F) · lnQ. Since Q = K eq at equilibrium, this equation can be used to calculate K eq , given E ̊ cell .
• One application of this is in determining the solubility product constant (K sp ) of a compound.
• First, E ̊ cell must be calculated by breaking the reaction into half-reactions. Once this calculation has been made, finding K sp is simply a matter of plugging the numbers into the formula.

Question 3

Which would best determine the equilibrium constant inside the cells of a car battery?

Answer 3

[H + ] and [HSO4− ]

Question 4

Which best describes the reaction that occurs when a car battery discharges?

Answer 4

Oxidation-reduction

Question 5

Which of the following is the oxidation half-reaction when a battery is discharging?

Answer 5

Pb(s) + HSO4− (aq) → PbSO4(s) + H + (aq) + 2e−

Question 6

Which type of reaction occurs inside the cells of a car battery?

Answer 6

Oxidation

Question 7

When does equilibrium occur in a battery?

Answer 7

Ecell = 0

Question 8

Which best describes the relationship between the reaction quotient and the voltage of a car battery?

Answer 8

↓ Q: ↑ battery potential

Question 9

Which of the following types of data have a triangular relationship?

Answer 9

Composition, electrochemical, and calorimetric

Question 10

Which best represents an oxidation half-reaction?

Answer 10

Ag → Ag+ + e−

Question 11

Which trends best describes what happens when a car battery discharges?

Answer 11

↓[H+] and ↓[HSO4-]

↑Q:↓ battery potential

Question 12

How many half-reactions occur when a car battery discharges?

Answer 12

Two

Question 13

Calculate the equilibrium constant for the following reaction at 25°C, given that
E°cell = +0.99 V

3Cu(s) + Cr2O72-(aq) + 14H+(aq) –> 3Cu2+(aq) + 2Cr3+(aq) + 7H2O(l)

Answer 13

2.18 × 10^100