± Introduction to the Nernst Equation Learning Goal: To learn how to use the Ner

Question

± Introduction to the Nernst Equation

Learning Goal:

To learn how to use the Nernst equation.

E=E2.303RTnFlog10Q

Substituting each constant into the equation the result is

E=E0.0592 Vnlog10Q

Mg(s)+Fe2+(aq)Mg2+(aq)+Fe(s)

at 69 C , where [Fe2+]= 3.60 M and [Mg2+]= 0.110 M .

Part A

What is the value for the reaction quotient, Q, for the cell?

Express your answer numerically.

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Part B

What is the value for the temperature, T, in kelvins?

Express your answer to three significant figures and include the appropriate units.

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Part C

What is the value for n?

Express your answer as an integer and include the appropriate units (i.e. enter mol for moles).

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Part D

Mg(s)+Fe2+(aq)Mg2+(aq)+Fe(s)

Express your answer to three significant figures and include the appropriate units.

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Part E

This question will be shown after you complete previous question(s).

± Introduction to the Nernst Equation

Learning Goal:

To learn how to use the Nernst equation.

The standard reduction potentials listed in any reference table are only valid at standard-state conditions of 25 C and 1 M. To calculate the cell potential at non-standard-state conditions, one uses the Nernst equation,

E=E2.303RTnFlog10Q

where E is the potential in volts, E is the standard potential in volts, R=8.314J/(Kmol) is the gas constant, Tis the temperature in kelvins, n is the number of moles of electrons transferred, F=96,500C/(mol e) is the Faraday constant, and Q is the reaction quotient.

Substituting each constant into the equation the result is

E=E0.0592 Vnlog10Q

Consider the reaction

Mg(s)+Fe2+(aq)Mg2+(aq)+Fe(s)

at 69 C , where [Fe2+]= 3.60 M and [Mg2+]= 0.110 M .

Part A

What is the value for the reaction quotient, Q, for the cell?

Express your answer numerically.

Q =

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Part B

What is the value for the temperature, T, in kelvins?

Express your answer to three significant figures and include the appropriate units.

T =

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Part C

What is the value for n?

Express your answer as an integer and include the appropriate units (i.e. enter mol for moles).

n =

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Part D

Calculate the standard cell potential for

Mg(s)+Fe2+(aq)Mg2+(aq)+Fe(s)

Express your answer to three significant figures and include the appropriate units.

E =

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Part E

This question will be shown after you complete previous question(s).

Explanation / Answer

Part A

Q = [product] / [reactant]

Q = [0.11] / [3.6]

Q = 3.06 x 10-2

Part B

T = 273.15 + 69 K = 342.15 K

Part C

n = 2 , n = number of electron transfered in the reaction

part D

E0 = Mg2+ / Mg = -2.37 V

E0 = Fe2+ / Fe = -0.44 V

E0 rxn = +2.37 - 0.44 = + 1.93 V (note : Mg oxidised to Mg2+ so +2.37 V)

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