Electrochemistry · Question 7

From the following select the one which is not an example of corrosion.

1. Rusting of iron object
2. Production of hydrogen by electrolysis of water
3. Tarnishing of silver
4. Development of green coating on copper and bronze ornaments

The standard cell potential of the following cell Zn | Zn2+(aq) || Fe2+(aq) | Fe is 0.32 V. Calculate the standard Gibbs energy change for the reaction: Zn(s) + Fe2+(aq) Zn2+(aq) + Fe(s) (Given : 1 F = 96487 C)

1. -61.75 kJ mol-1
2. +5.006 kJ mol-1
3. -5.006 kJ mol-1
4. +61.75 kJ mol-1

The conductivity of centimolar solution of KCl at 25 is 0.0210 ohm-1 cm-1 and the resistance of the cell containing the solution at 25 is 60 ohm. The value of cell constant is -

1. 3.28 cm-1
2. 1.26 cm-1
3. 3.34 cm-1
4. 1.34 cm-1

Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R: In the light of the above statements, choose the correct answer from the options given below:

1. Both A and R are true but R is NOT the correct explanation of A.
2. A is true but R is false.
3. A is false but R is true.
4. Both A and R are true and R is the correct explanation of A.

At 298 K, the standard electrode potentials of Cu2+/Cu, Zn2+/Zn, Fe2+/Fe and Ag+/Ag are 0.34 V, -0.76 V, -0.44 V and 0.80 V, respectively. On the basis of standard electrode potential, predict which of the following reaction cannot occur?

1. CuSO4(aq) + Zn(s) ZnSO4(aq) + Cu(s)
2. CuSO4(aq) + Fe(s) FeSO4(aq) + Cu(s)
3. FeSO4(aq) + Zn(s) ZnSO4(aq) + Fe(s)
4. 2CuSO4(aq) + 2Ag(s) 2Cu(s) + Ag2SO4(aq)

Given below are half cell reactions: MnO4- + 8H+ + 5e- Mn2+ + 4H2O, E Mn2+/MnO4- = -1.510 V 12O2 + 2H+ + 2e- H2O E O2/H2O = +1.223 V Will the permanganate ion, MnO4- liberate O2 from water in the presence of an acid?

1. Yes, because E cell = +0.287 V
2. No, because E cell = -0.287 V
3. Yes, because E cell = +2.733 V
4. No, because E cell = -2.733 V

Find the emf of the cell in which the following reaction takes place at 298 K Ni(s) + 2Ag+ (0.001 M) Ni2+ (0.001 M) + 2Ag(s) (Given that E cell = 1.05 V, 2.303 RTF = 0.059 at 298 K)

1. 1.0385 V
2. 1.385 V
3. 0.9615 V
4. 1.05 V

Two half cell reactions are given below. Co3+ + e- Co2+, E0 Co2+/Co3+ = -1.81 V 2Al3+ + 6e- 2Al(s), E0 Al/Al3+ = +1.66 V The standard EMF of a cell with feasible redox reaction will be :

1. -3.47 V
2. +7.09 V
3. +0.15 V
4. +3.47 V

Standard electrode potential for the cell with cell reaction Zn(s) + Cu2+(aq) Zn2+(aq) + Cu(s) is 1.1 V. Calculate the standard Gibbs energy change for the cell reaction. (Given F = 96487 C mol-1)

1. -200.27 J mol-1
2. -200.27 kJ mol-1
3. -212.27 kJ mol-1
4. -212.27 J mol-1

The molar conductance of NaCl, HCl and CH3COONa at infinite dilution are 126.45, 426.16 and 91.0 S cm2 mol-1 respectively. The molar conductance of CH3COOH at infinite dilution is. Choose the right option for your answer.

1. 540.48 S cm2 mol-1
2. 201.28 S cm2 mol-1
3. 390.71 S cm2 mol-1
4. 698.28 S cm2 mol-1