Important Questions of Electrochemistry Chemistry | Zigya

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31.

Consider the following E° values

straight E subscript Fe to the power of 3 plus end exponent divided by Fe to the power of 2 plus end exponent end subscript superscript straight o space equals space 0.77 space straight V
straight E subscript Sn to the power of 2 plus end exponent divided by Sn end subscript superscript straight o space equals space minus 0.14
Under standard conditions the potential for the reaction
Sn(s) + 2Fe3+(aq) → 2Fe2+(aq) + Sn2+(aq) is

  • 1.68 V

  • 0.63 V

  • 0.91 V

  • 0.91 V

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32.

The standard e.m.f of a cell, involving one electron change is found to be 0.591 V at 25°C. The equilibrium constant of the reaction is (F = 96,500 C mol-1: R = 8.314 JK-1 mol-1)

  • 1.0×101

  • 1.0×1030

  • 1.0×1030

  • 1.0×1030

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33.

The limiting molar conductivities Λ° for NaCl, KBr and KCl are 126, 152 and 150 S cm2 mol-1 respectively. The Λ° for NaBr is

  • 128 S cm2 mol-1

  • 302 S cm2 mol-1

  • 278 S cm2 mol-1

  • 278 S cm2 mol-1

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34.

In a cell that utilises the reaction Zn(s) + 2H+ (aq) → Zn2+(aq) + H2(g) addition of H2SO4 to cathode compartment, will

  • lower the E and shift equilibrium to the left

  • increases the E and shift equilibrium to the left

  • increase the E and shift equilibrium to the right

  • increase the E and shift equilibrium to the right

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35.

The straight E subscript straight M to the power of 3 plus end exponent divided by straight M to the power of 2 plus end exponent end subscript superscript straight o values for Cr, Mn, Fe and Co are – 0.41, +1.57, + 0.77 and +1.97 V respectively. For which one of these metals the change in oxidation state form +2 to +3 is easiest?

  • Cr

  • Co

  • Fe

  • Fe

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36.

How long (approximate) should water be electrolysed by passing through 100 amperes current so that the oxygen released can completely burn 27.66 g of diborane? (Atomic weight of B = 10.8 u)

  • 1.6 hours

  • 6.4 hours

  • 0.8 hours

  • 3.2 hours


37.

During electrolysis of molten NaCl, some water was added. What will happen?

  • Electrolysis will stop

  • Hydrogen will be evolved

  • Some amount of caustic soda will be formed

  • A fire is likely


38.

The role of fluorspar, which is added in small quantities in the electrolytic reduction of alumina dissolved in fused cryolite is

  • as a catalyst

  • to make fused mixture conducting

  • to lower the melting temperature of the mixture

  • to decrease the rate of oxidation of carbon at anode


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39.

At temperature of 298K, the emf of the following electrochemical cell,

Ag (s) | Ag+ (0.1 M)|| Zn2+ (0.1 M) | Zn (s)

will be (Given, E°cell = -1.562 V)

  • -1.532 V

  • -1.503 V

  • 1.532 V

  • -3.06 v


40.

The quantity of electricity needed to separately electrolyze 1 M solution of ZnSO4 , AlCl3 and AgNO3 completely is in the ratio of

  • 2 : 3 :1

  • 2 : 1 : 1

  • 2 : 1:3

  • 2 : 2 : 1


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