In: Chemistry
Consider the reaction
Mg(s)+Fe2+(aq)→Mg2+(aq)+Fe(s)
at 63 ∘C , where [Fe2+]= 2.90 M and [Mg2+]= 0.210 M .
Part A
What is the value for the reaction quotient, Q, for the cell?
Express your answer numerically.
Q = |
7.24×10−2 |
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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 = |
336 K |
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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 = |
2 mol |
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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∘ = |
1.92 V |
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Part E
What is the cell potential for the reaction
Mg(s)+Fe2+(aq)→Mg2+(aq)+Fe(s)
at 63 ∘C when [Fe2+]= 2.90 M and [Mg2+]= 0.210 M .
Part A
What is the value for the reaction quotient, Q, for the cell?
Express your answer numerically.
Solution :- reaction quotient Q is calculated as follows
Q= [product]/[reactant]
Q= [Mg2+]/[Fe2+]
Q= 0.210 /2.90
Q= 7.24*10-2
Part B
What is the value for the temperature, T, in kelvins?
Express your answer to three significant figures and include the appropriate units.
Solution :-
T in Kelvin = T in Celcius + 273
= 63 C +273
= 336 K
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).
Solution :-
N is nothing but the number of electrons transferred in the reaction
Therefore for the given reaction n=2
Because 2 electrons transferred.
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.
Solution :-
Standard cell potential is calculated as
Eo Cell = Eo cathode – Eo anode
For the given reaction Mg chaning to Mg2+ is the anode reaction and Fe2+ chaning to Fe is the cathode reaction.
Using the standard reduction potential we can calculate the Eo cell
Standard reduction potential for the Mg2+ = -2.36 V and for Fe2+ = -0.44 V
Eo Cell = Eo cathode – Eo anode
= -0.44 V - (-2.36 V)
= 1.92 V
Part E
What is the cell potential for the reaction
Mg(s)+Fe2+(aq)→Mg2+(aq)+Fe(s)
at 63 ∘C when [Fe2+]= 2.90 M and [Mg2+]= 0.210 M
Solution :-
Formula to calculate the cell potential Ecell is as follows
E cell = Eo Cell – (RT/nF)lnQ
Where R = 8.314 J per mol K
n = number of electrons transferred
F= faradays constant = 96485 C/mol
Q = reaction quotient
T= Kelvin temperature
Now lets put the values in the formula and calculate cell potential
E cell = 1.92 V – (8.314 J per mol K * 336 K/2*96485 C per mol ) ln [7.24*10-2]
= 1.92 V – (-0.038)
= 1.96 V
Therefore Ecell = 1.96 V