17.6

To find cell potential, we simply compute:

Ecathode−Eanode

For a galvanic cell to generate an electric current spontaneously, what must be true?

Ecell must be positive

The term electrical work best fits which of the following descriptions?

Electrical work is the negative of the product of total charge and cell potential.

In order to derive a simplified version of the Nernst equation by assuming standard temperature, we can substitute which of the following into the general equation?

Faraday's constant 298 K

Which description best fits the definition of Faraday's constant?

Faraday's constant is the charge of 1 mol of electrons.

In order to derive the Nernst equation, what modification must be made to the free energy equation?

Gibbs free energy is expressed in terms of cell potential.

For the reaction below: PCl5(g)↽−−⇀PCl3(g)+Cl2(g) The equilibrium constant K is found to be 1.0×10−3. What is ΔG∘ (in kilojoules per mole) for this reaction at 298 K?

17

Consider the following reaction proceeding at 298.15 K: 2Al(s)+3Cu2+(aq,1.70 M)⟶2Al3+(aq, 0.00560 M)+3Cu(s) If the standard reduction potential for copper(II) is 0.340 V and the standard reduction potential for aluminum is −1.66 V, what is the cell potential for this cell, in volts?

2.1 V

What must be true of a system where reactants and products are equally abundant at equilibrium, if the reaction is A + B --> C + D?

Keq=1, ΔG=0

For the following reaction at room temperature, what is [Zn2+] when Ecell=1.05V? Zn(s)+Cu2+(aq,0.00500M)⟶Zn2+(aq,?M)+Cu(s) anode (oxidation):Zn(s)⟶Zn2+(aq)+2e−E∘Zn2+/Zn=−0.760 Vcathode (reduction):Cu2+(aq)+2e−⟶Cu(s)E∘Cu2+/Cu=0.340 V

.244 M

Consider the following reaction proceeding at 298.15 K: Cu(s)+2Ag+(aq,0.15 M)⟶Cu2+(aq, 1.14 M)+2Ag(s) If the standard reduction potential for copper(II) is 0.34 V and the standard reduction potential for silver(I) is 0.80 V what is the cell potential for this cell, in volts?

.41

What is the standard cell potential (in volts) for the reaction below that has ΔG∘=−86.8kJ at 25∘C? Zn(s)+Cl2(g)↽−−⇀Zn2+(aq)+2Cl−(aq)

.450 V

A galvanic cell at room temperature has a standard cell potential of 0.64 V and contains a reaction that involves the transfer of one mole of electrons, with a reaction quotient of 9.10. What will be its cell potential in volts?

.58 V

A galvanic cell involving the transfer of two moles of electrons has an equilibrium constant of 2.4. What is the electrical potential (in volts) in this cell under standard conditions? Use the simplified equation below. E∘cell=(0.0592 V/n)logKeq

0.011

For the following reaction at room temperature, what is [Zn2+] when Ecell=1.14V? Zn(s)+Cu2+(aq,1.50M)⟶Zn2+(aq,?M)+Cu(s) anode (oxidation):Zn(s)⟶Zn2+(aq)+2e−E∘Zn2+/Zn=−0.76 Vcathode (reduction):Cu2+(aq)+2e−⟶Cu(s)E∘Cu2+/Cu=0.34 V Report your answer with two significant figures.

0.067 M

Consider the following reaction proceeding at 298.15 K: Fe(s)+Cu2+(aq,1.87 M)⟶Fe2+(aq, 0.19 M)+Cu(s) If the standard reduction potential for copper(II) is 0.34 V and the standard reduction potential for iron(II) is -0.41 V, what is the cell potential (in V) for this cell?

0.78 V

A galvanic cell at room temperature with a standard cell potential of 0.84 V, which transfers three moles of electrons and is associated with a reaction quotient of 276.00, will have a cell potential of what value (in volts)?

0.79

A galvanic cell at 25∘C has a standard cell potential of 1.26 V. The reaction in the cell involves the transfer of two moles of electrons and has a reaction quotient of 463.000. What is the cell potential, in volts?

1.18 V

At −73∘C, the process X⟶Y+Z has a standard free energy change of 11.5kJmol. What is the free energy change (in kilojoules per mole) at the same temperature with [X]=0.65 M, [Y]=1.8M, and [Z]=2.5M? The universal gas constant is 8.314Jmol K.

14.7

The Nernst equation shows that nonstandard cell potential depends on:

the reaction quotient

Which of the following affects cell potential?

the standard cell potential

If we plug R, F, and room temperature (298.15 K) for T into the equation relating standard cell potential and the equilibrium constant, we arrive at an equation that relates E∘cell to

(0.0257 V/n)logKeq

At standard temperature, the Nernst equation can be rewritten to show that the nonstandard cell potential is equal to the standard cell potential minus:

(0.0592 V/n)lnQ

Consider the following reaction: Co(s)+Fe2+(aq,1.47 M)⟶Co2+(aq,0.33 M)+Fe(s) If the standard reduction potential for cobalt(II) is −0.28 V and the standard reduction potential for iron(II) is −0.447 V, what is the cell potential in volts for this cell?

-0.15

At 50.0∘C, the process X+Y⟶Z has a standard free energy change of 45.0kJmol. What is the free energy change (in kilojoules per mole) at the same temperature when with [X]=0.15 M, [Y]=0.46 M, and [Z]=0.33 M? The universal gas constant is 8.314Jmol K.

49.2

The units of the gas constant typically used in the Nernst equation is:

8.314 J/mol K

Cell potential, when calculated using the Nernst equation, depends on:

all of the above

Which of the following are related by a known equation?

all of the above

the Nernst equation depends on:

all of the above

standard free energy depends on

all the above

For a galvanic cell where the standard free energy change is negative and the cell potential is positive, the reaction in the cell must be:

always spontaneous

When considering the relationship among standard free energy change, equilibrium constants, and standard cell potential, the equation ΔG∘=−RTlnK is _______.

used to find the equilibrium constant given the standard free energy change

Standard free energy change is:

directly proportional to E∘cell

Standard cell potential is:

directly proportional to the natural log of K

The equation E∘cell=(RT/nF)lnK is _______.

used to find the standard cell potential given the equilibrium constant

The Nernst equation allows us to calculate:

galvanic cell potential under nonstandard conditions

If ΔG∘>0, _______.

reactants are more abundant at equilibrium

When considering the relationship among standard free energy change, equilibrium constants, and standard cell potential, the equation ΔG∘=−nFE∘cell is _______.

used to find the standard free energy change given the standard cell potential

If K>1, _______.

ΔG∘ is negative

What must be true about galvanic cells with spontaneous reactions?

ΔG∘<0, E∘cell>0

Choose the option below that is not necessarily true of a system at equilibrium.

ΔG∘=0

What is the standard free energy change at 25∘C? Cu2+(aq)+Zn(s)⟶Cu(s)+Zn2+(aq) anode (oxidation): Zn(s)⟶Zn2+(aq)+2e−E∘Zn2+/Zn=−0.76 Vcathode (reduction): Cu2+(aq)+2e−⟶Cu(s)E∘Cu2+/Cu=0.34V

−212.3kJ/mol