The standard half-cell reduction potential for Ag+| Ag is 0.7991

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 Multiple Choice QuestionsMultiple Choice Questions

341.

Assertion : Sodiumacetate on Kolbe's electrolysis gives methane.

Reason : Methyl free radical is formed at cathode.

  • If both assertion and reason are true and reason is the correct explanation of assertion.

  • If both assertion and reason are true but reason is not the correct explanation of assertion.

  • If assertion is true but reason is false.

  • If both assertion and reason are false.


342.

Assertion : Magnesium is extracted by the electrolysis of fused mixture of MgCl2, NaCl and CaCl2.

Reason : Calcium chloride acts as a reducing agent.

  • If both assertion and reason are true and reason is the correct explanation of assertion.

  • If both assertion and reason are true but reason is not the correct explanation of assertion.

  • If assertion is true but reason is false.

  • If both assertion and reason are false.


343.

If a salt bridge is removed between the half cells , the voltage :

  • decreases to zero

  • increases

  • increases rapidly

  • do not change


344.

During electrochemical process :

  • Gibbs free energy increases

  • Gibbs free energy remains constant

  • no prediction can' be made about Gibbs free energy

  • Gibbs free energy decreases


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345.

A factory produces 40 kg of calcium in two hours by electrolysis. How much aluminium can be produced by same current in 2 hours if current efficiency is 50%?

  • 22 kg

  • 18 kg

  • 9 kg

  • 27 kg


346.

The standard emf of a cell , involving one electron change is found to be 0.591 V at 25o C . The equilibrium constant of the reaction is :

(F = 96500 C mol-1 , R = 8.314 JK-1mol-1)

  • 1.0 x 101

  • 1.0 x 105

  • 1.0 x 1010

  • 1.0 x 1030


347.

A complex PtCl4.5NH3, shows a molar conductance of 402 ohm-1 cm2mol-1 in water and precipitates three moles ofAgCl with AgNOsolution. The formula of the complex is

  • [Pt(NH3)6]Cl4

  • [Pt(NH3)4Cl2]Cl2

  • [Pt(NH3)5Cl]Cl3

  • [Pt(NH3)3Cl3]Cl


348.

Calculate HOAC using appropriate molar conductances of the electrolytes listed above at infinite dilution in H2O at 25°C.
Electrolyte  KCl  KNO3  HCL  NaOAc  NaCl
  S cm2mol-1  149.9  145.0  426.2  91.0  126.5

  • 517.2

  • 552.7

  • 390.7

  • 217.5


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349.

The standard half-cell reduction potential for Ag+| Ag is 0.7991 V at 25°C. Given the experimental value Ksp= 1.56 x 10-10 for AgCl, calculate the standard half-cell reduction potential for the Ag | AgCl electrode.

  • 0.2192V

  • -0.2192V

  • -1.2192 V

  • 1.2192 V


A.

0.2192V

For the desired reaction,

AgCl + 1e-  Ag + Cl-, E° =-rG°(1)F

The needed rG° can obtained by adding the value of rG° for the reactions

Ag+ + 1e-  Ag; G° = -nFE°

AgCl  Ag+ + Cl ; G° = -RT ln  Ksp, giving

rG° =-( 1mol)(9.648 ×104 J mol-1 V-1)(0.7991V)-(8.314 JK-1mol-1)(298k)ln(1.56 × 10-10) = -77.10kJ+ 55.95 kJ = -21.15 kJ

The potential is E°=-(-21.15)(1)(96.485) =+0.2192 V.


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350.

Assertion : Reduction potential of Mn (+3 to +2) is more positive than Fe (+3 to +2).

Reason: Ionisation potential of Mn is more than that of Fe.

  • If both assertion and reason are true and reason is the correct explanation of assertion

  • If both assertion and reason are true but reason is not the correct explanation of assertion

  • If assertion is true but reason is false

  • If both assertion and reason are false.


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