Question

A student made measurements on some electrochemical cells and calculated three quantities: • The standard reaction free energy AGO. • The equilibrium constant K at 25.0°c. • The cell potential under standard conditions E. His results are listed below. Unfortunately, the student may have made some mistakes. Examine his results carefully and tick the box next to the incorrect quantity in each row, if any. Note: If there is a mistake in a row, only one of the three quantities listed is wrong. Also, you may assume the number of significant digits in each quantity is Also note: for each cell, the number n of electrons transferred per redox reaction is 1. correct. calculated quantities (Check the box next to any that are wrong.) cell AG K A 1 -19. J/molo -0.20 V OO B 2.13 x 10 -24 592 x 10 21 5.30 x 10 -144. J/mol -1.49 V o c 1 124. J/mol o -1.29 V X

Answer 1

Hi there,

We have to take ΔG0 value and check K & E0 values are consistenet or not

ΔG⁰ = -RTlnK ==> K = e^-(ΔG0/RT)

ΔG⁰ = -nFE⁰ ==> E⁰ = -ΔG⁰ / nF

ΔG⁰ = in J/mol

R = 8.3145 J/mol.K

T = 25 = 25 + 273.15 = 298.15 K

n = 1e^-

F = faraday's constant = 96485 C/mol.e^-

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A:

ΔG⁰ = -19 kJ/mol = -19000 J/mol

K = e^-(ΔG0/RT) = K = e^{-(-19000J/mol / (8.3145 J/mol.K x 298.15 K )} = 2131.28250824 = 2.13 x 10³

E⁰ = -ΔG⁰ / nF = -(-19000 J.mol.K) / (1e^- x 96485 C/mol.e^-) = 0.19692180131 = 0.20 V (This is + sign) given option is negative sign

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B:

ΔG⁰ = -144 kJ/mol = -144000 J/mol

K = e^-(ΔG0/RT) = K = e^{-(-144000J/mol / (8.3145 J/mol.K x 298.15 K )} = 1.6888657e+25 = 1.69 x 10²⁵

E⁰ = -ΔG⁰ / nF = -(-144000 J.mol.K) / (1e^- x 96485 C/mol.e^-) = 1.49245996787 = +1.49 V

Actuall both K & E⁰ values are wrong, but they clearly mentioned that only one of the three values is wrong and when you choose in a row, so neglect negative sign for cell potential still number is correct, but K is entirely wrong.

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C:

ΔG⁰ = 124 kJ/mol = 124000 J/mol

K = e^-(ΔG0/RT) = K = e^{-(124000J/mol / (8.3145 J/mol.K x 298.15 K )} = 1.8890243e-22 = 1.89 x 10^-22

E⁰ = -ΔG⁰ / nF = -(124000 J.mol.K) / (1e^- x 96485 C/mol.e^-) = 1.28517386122 = -1.29 V

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A student made measurements on some electrochemical cells and calculated three quantities: • The standard reaction free energy AGO. . The equilibrium constant K at 25.0 °C. • The cell potential under standard conditions E. His results are listed below. Unfortunately, the student may have made some mistakes. Examine his results carefully and tick the box next to the incorrect quantity in each row, if any. Note: If there is a mistake in a row, only one of the three quantities listed is wrong. Also, you may assume the number of significant digits in each quantity is Also note: for each cell, the number n of electrons transferred per redox reaction is 1. correct. calculated quantities (Check the box next to any that are wrong.) cell AG K A 1 -19. /mol 2.13 x 10 O -0.20 V B -144. J/molo 5.92 x 10 -1.49 V Select RED colored boxes as wrong D c 1 124 W/mol 5.30 x 10 -1.29 V х

Hope this helped you!

Thank You So Much!

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