Electrochemistry

Calculate emf of the half cell given below : Pt(s) | H2(g, 2 atm) | HCl(aq, 0.02 M) E H2/H+ = 0 V (Given : 2.303RTF = 0.059, log 2 = 0.3010)

1. −0.109 V
2. 0.109 V
3. 0.035 V
4. −0.035 V

A solution of copper sulphate is electrolysed for 10 minutes with a current of 1.5 amperes. The mass of copper deposited at cathode is : (Given : Molar mass of Cu = 63 g mol-1; 1F = 96487 C mol-1)

1. 0.2938 g
2. 0.5876 g
3. 2.4036 g
4. 1.7018 g

The standard electrode potential (E ) for the half-cell reaction Fe3+ + e- Fe2+ at 298 K is (Given : E ( Fe3+/Fe) = -0.04 V and E ( Fe2+/Fe) = -0.44 V at 298 K)

1. +0.92 V
2. +0.40 V
3. +0.76 V
4. -0.48 V

For a salt XY, which is a strong electrolyte, the plot of m versus c has a slope of -90.0 S cm2 mol-3/2 L1/2 at 298 K. At 0.01 M concentration of XY, the value of m is 145.0 S cm2 mol-1. The limiting molar conductivity of Y- ion ( Y-0, in S cm2 mol-1) at 298 K will be (Given : X+0 = 74.0 S cm2 mol-1)

1. 76.0
2. 80.0
3. 100.0
4. 90.0

If the molar conductivity ( m) of a 0.050 mol L-1 solution of a monobasic weak acid is 90 S cm2 mol-1, its extent (degree) of dissociation will be [Assume + = 349.6 S cm2 mol-1 and - = 50.4 S cm2 mol-1.]

1. 0.225
2. 0.215
3. 0.115
4. 0.125

Mass in grams of copper deposited by passing 9.6487 A current through a voltameter containing copper sulphate solution for 100 seconds is (Given : Molar mass of Cu: 63 g mol-1, 1 F = 96487 C)

1. 3.15 g
2. 0.315 g
3. 31.5 g
4. 0.0315 g

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

The molar conductivity of 0.007 M acetic acid is 20 S cm2 mol-1. What is the dissociation constant of acetic acid? Choose the correct option. [ H+ = 350 S cm2 mol-1 CH3COO- = 50 S cm2 mol-1]

1. 2.50 10-5 mol L-1
2. 1.75 10-4 mol L-1
3. 2.50 10-4 mol L-1
4. 1.75 10-5 mol L-1

On electrolysis of dil. sulphuric acid using Platinum (Pt) electrode, the product obtained at anode will be :

1. Oxygen gas
2. H2S gas
3. SO2 gas
4. Hydrogen gas

The number of Faradays(F) required to produce 20 g of calcium from molten CaCl2 (Atomic mass of Ca = 40 g mol-1) is :

1. 2
2. 3
3. 4
4. 1

For a cell involving one electron E cell = 0.59 V at 298 K, the equilibrium constant for the cell reaction is : [Given that 2.303 RTF = 0.059 V at T = 298 K]

1. 1.0 1030
2. 1.0 1010
3. 1.0 102
4. 1.0 105

For the cell reaction 2Fe3+(aq) + 2I-(aq) 2Fe2+(aq) + I2(aq) E cell = 0.24 V at 298 K. The standard Gibbs energy ( r G ) of the cell reaction is : [Given that Faraday constant F = 96500 C mol-1]

1. 46.32 kJ mol-1
2. 23.16 kJ mol-1
3. -46.32 kJ mol-1
4. -23.16 kJ mol-1

In the electrochemical cell : Zn | ZnSO4 (0.01 M) || CuSO4 (1.0 M) | Cu, the emf of this Daniell cell is E1. When the concentration of ZnSO4 is changed to 1.0 M and that of CuSO4 changed to 0.01 M, the emf changes to E2. From the following, which one is the relationship between E1 and E2? (Given, 2.303RTF = 0.059)

1. E1 < E2
2. E1 > E2
3. E2 = 0 E1
4. E1 = E2

The pressure of H2 required to make the potential of H2-electrode zero in pure water at 298 K is

1. 10-10 atm
2. 10-4 atm
3. 10-14 atm
4. 10-12 atm

The molar conductivity of a 0.5 mol/dm3 solution of AgNO3 with electrolytic conductivity of 5.76 10-3 S cm-1 at 298 K is

1. 2.88 S cm2/mol
2. 11.52 S cm2/mol
3. 0.086 S cm2/mol
4. 28.8 S cm2/mol

During the electrolysis of molten sodium chloride, the time required to produce 0.10 mol of chlorine gas using a current of 3 amperes is

1. 55 minutes
2. 110 minutes
3. 220 minutes
4. 330 minutes

If the E cell for a given reaction has a negative value, which of the following gives the correct relationships for the values of G and Keq ?

1. G > 0; Keq < 1
2. G > 0; Keq > 1
3. G < 0; Keq > 1
4. G < 0; Keq < 1

The number of electrons delivered at the cathode during electrolysis by a current of 1 ampere in 60 seconds is (charge on electron = 1.60 10-19 C)

1. 6 1023
2. 6 1020
3. 3.75 1020
4. 7.48 1023

Zinc can be coated on iron to produce galvanized iron but the reverse is not possible. It is because

1. zinc is lighter than iron
2. zinc has lower melting point than iron
3. zinc has lower negative electrode potential than iron
4. zinc has higher negative electrode potential than iron

Aqueous solution of which of the following compounds is the best conductor of electric current ?

1. Hydrochloric acid, HCl
2. Ammonia, NH3
3. Fructose, C6H12O6
4. Acetic acid, C2H4O2

A device that converts energy of combustion of fuels like hydrogen and methane, directly into electrical energy is known as

1. dynamo
2. Ni-Cd cell
3. fuel cell
4. electrolytic cell