The standard emf of the cell , Zn_{(s)}|Zn^{2+}_{(aq)}||Fe^{3+}_{(aq)},Fe^{2+}_{(aq)}| Pt at 25° C is 1.53 V and at 50° C is 1.55 V The value of ΔS° for the overall reaction is

Correct Answer is : 154.4 JK−1

JEE Advanced Model Paper 8 with solutions for online practice

Paragraph for Questions Nos. 14 to 16

Electrical energy produced by a reversible electrochemical cell is given by the free energy decrease (-ΔG) of the reaction occurring in the cell. According to Gibbs- Helmholtz equation, decrease in freeenergy is given by -ΔG = -ΔH - T [

δ(ΔG)

δT

]p where -ΔH is the decrease in enthalpy of the cell reaction at constant pressure. EMF of the cell, E =

−ΔH

+ T [

δE

δT

]p . By measuring the emf of the cell and its temperature co-efficient,thermodynamic quantities like ΔH, ΔG and ΔS can be determined. Standard emf of the cell is related to equilibrium constant of the cell reaction as E° =

2.303RTlogk

Question : 16 of 84

Marks: +1, -0

The standard emf of the cell , Z

(s)

n2+

(aq)

||F

e3+

(aq)

e2+

(aq)

| Pt at 25° C is 1.53 V and at 50° C is 1.55 V
The value of ΔS° for the overall reaction is

154.4 JK−1
-154.4 JK−1
154.4 KJK−1
77.2 JK−1

Validate

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