Electrode Potential and Standard Electrode Potential

IMPORTANT

Electrode Potential and Standard Electrode Potential: Overview

This Topic covers sub-topics such as Electrode Potential, Standard Hydrogen Electrode, Calomel Electrode, Reference Electrodes, Measurement of EMF of a Cell, Reduction Electrode Potential and, Standard Reduction Electrode Potential

Important Questions on Electrode Potential and Standard Electrode Potential

MEDIUM
IMPORTANT

Two half-reactions of an electrochemical cell are given below :

 MnO4(aq)+8H+(aq)+5eMn2+(aq)+4H2O(l), E°=+1.51V

 Sn2+(aq)Sn4+(aq)+2e,E°=+0.15V

What is the standard cell potential?

EASY
IMPORTANT

Two half-cell reactions of an electrochemical cell are given below :

 MnO4(aq)+8H+(aq)+5eMn2+(aq)+4​ H2O(l),E°=1.51V

 Sn2+(aq)Sn4+(aq)+2eE°=+0.15V

What would be the final cell potential?

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A copper-silver cell is set up. The copper ion concentration in it is 0.10 M. The concentration of silver ion is not known. The cell potential measured is 0.422 V. Determine the concentration of silver ion in the cell. Given :  EAg+/Ago=+0.80 V, ​ ECu2+/Cuo=+0.34​ V.

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An acidic solution of Cu2+salt containing 0.4gofCu2+is electrolysed until all the copper is deposited. The electrolysis is continued for seven more minutes with the volume of solution kept at 100 mL and the current at 1.2 amp. The volume of gases evolved at NTP during the entire electrolysis:

MEDIUM
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A solution containing one mole per litre of each   Cu ( N O 3 ) 2 ;AgN O 3 ;H g 2 ( N O 3 ) 2 ;  is being electrolysed by using inert electrodes. The values of standard electrode potentials in volts are :

 Ag/Ag+=+0.80,  Hg2/Hg22+=+0.79Cu/Cu2+=+0.34,  Mg/Mg2+=2.37

With increasing voltage, the sequence of deposition of metals on the cathode will be :

MEDIUM
IMPORTANT

The equilibrium constant for the reaction,  2Fe3++3I2Fe2++I3 would be, if the standard reduction potentials in acidic conditions are 0.77 V and 0.54 V respectively for  Fe3+/Fe2+andI3/Icouple.

HARD
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The standard potential of the following cell is 0.23 V at   15°C  and 0.21 V at   35°C .

 Pts|H2(g)|HCl(aq)|AgCl(s)|Ag(s)

 (ii) Calculate   ΔH°andΔS°  for the cell reaction by assuming that these quantities remain unchanged in the range 15°C to 35°C.

(iii) Calculate the solubility of AgCl in water at   25°C .

Given: The standard reduction potential of the  Ag+(aq)/Ag(s)  couple is 0.80 V at 25°C.

MEDIUM
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A standard hydrogen electrode has zero electrode potential because

HARD
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The emf of the cell:

Zn|Zn2+(0.01M)||Fe2+(0.001M)|Fe at 298 K is 0.2905 V. Then the value of equilibrium constant for the cell reaction is:

 

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Standard electrode potential data are useful for understanding the suitability of an oxidant in a redox titration. Some half cell reactions and their standard potentials are given below :

 MnO4(aq.)+8H+(aq,)+5eMn2+(aq.)+4H2O  (1)                                                                                                                                                          E°=1.51  VCr2O72(aq.)+14H+(aq.)+6e2Cr3+(aq.)+7H2O  (1)                                                                                                                                                           E°=1.38  VFe3+(aq.)+eFe2+(aq.)                                   E°=0.77  VCl2(g)+2e2Cl  (aq.)                                     E°1.40  V

Identify the only incorrect statement regarding the quantitative estimation of aqueous   Fe ( N O 3 ) 2

EASY
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When the samples of copper with zinc impurity is to be purified by electrolysis, the appropriate electrodes are –

MEDIUM
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Calculate Reduction Potential of hydrogen electrode at 298K which is prepared with the help of aq. solution of   acetic acid with 0.1 M conc at 1 atm pressure Ka = 1.8 x 10-5.

MEDIUM
IMPORTANT

The incorrect statements from the following is:
A. The electrical work that a reaction can perform at constant pressure and temperature is equal to the reaction Gibbs energy.
B. Ecell  is dependent on the pressure.
C. dEcell°dT=ΔrS°nF
D. A cell is operating reversibly if the cell potential is exactly balanced by an opposing source of potential difference.

MEDIUM
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Which of the following is oxidised by oxygen in acidic medium?

HARD
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For the galvanic cell : Ag|AgCl(s)|KCl(0.2M)||KBr(0.001M)|AgBr(s)|Ag, Calculate the EMF generated and assign correct polarity to each electrode for a spontaneous process after taking into account the cell reaction at 25°CKspAgCl=2.8×10-10;KspAgBr=3.3×10-13

MEDIUM
IMPORTANT

One of the most common cells that's been used in our daily life is Duracell, also known as an alkaline cell. The image below shows the internal structure of a Duracell.

Question Image

This cell uses a zinc half-cell and another half-cell containing a carbon (graphite) electrode in contact of moist manganese oxide. Given that the electrode potential for Zn2+/Zn= -0.76 V and Mn4+/Mn3+ (aq.) = +0.74V.

Which of the two will be the positive electrode and why?

HARD
IMPORTANT

One of the most common cells that's been used in our daily life is Duracell, also known as an alkaline cell. The image below shows the internal structure of a Duracell.

Question Image

This cell uses a zinc half-cell and another half-cell containing a carbon (graphite) electrode in contact of moist manganese oxide. Given that the electrode potential for Zn2+/Zn= -0.76 V and Mn4+/Mn3+ (aq.) = +0.74V.

Calculate the overall cell potential.

HARD
IMPORTANT

Which of the following facts is not true?

MEDIUM
IMPORTANT

The standard reduction potentials of some half cell reactions are given below :

PbO2+4H++2e-Pb2++2H2O  E0=1.455 V
MnO4-+8H++5e-Mn2++4H2O  E0=1.51 V
Ce4++e-Ce3+  E0=1.61 V
H2O2+2H++2e-2H2O  E0=1.71 V
Pick out the Incorrect statement :-