The standard reduction potential for Mg2+ /Mg is - 2.37 V and for

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 Multiple Choice QuestionsMultiple Choice Questions

71.

EMF of hydrogen electrode in term of pH is (at 1 atm pressure).

  • EH2=RTF×pH

  • EH2=RTF·1pH

  • EH2=2.303 RTFpH

  • EH2=- 0.591 pH


72.

For the cell reaction, 

2Ce4+ + Co → 2Ce3+ + Co3+; Ecell° is 1.89 V. If ECo2+/ Co is -0.28V, what is the value of ECe4+ / Ce3+°?

  • 0.28 V

  • 1.61 V

  • 2.17 V

  • 5.29 V


73.

The equivalent conductance of silver nitrate solution at 250°C for an infinite dilution was found to be 133.3 Ω-1 cm2 equiv-1. The transport number of Ag+ ions in very dilute solution of AgNO3 is 0.464. Equivalent conductances of Ag+ and NO3- (in Ω-1 cm2 equiv-1) at infinite dilution are respectively.

  • 195.2; 133.3

  • 61.9; 71.4

  • 71.4; 61.9

  • 133.3; 195.2


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74.

The standard reduction potential for Mg2+ /Mg is - 2.37 V and for Cu2+ /Cu is 0.337. The Ecell° for the following reaction is

Mg + Cu2+ → Mg2+ + Cu

  • +2.03 V

  • -2.03 V

  • -2.7 V

  • +2.7 V


D.

+2.7 V

Ecell° = Ecathode° - Eanode°         = E(Cu2+/ Cu)° - E(Mg2+ / Mg)°         = 0.337 - (-2.37) V         = 2.7 V


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75.

Cu+ (aq) is unstable in solution and undergoes simultaneous oxidation and reduction, according to the reaction

                    2Cu+(aq)  Cu+(aq) + Cu(s)

choose correct E° for above reaction if

ECu2+/Cu°= 0.34 V     andECu2+/Cu+° = 0.15 V

  • -0.38 V

  • + 0.49 V

  • + 0.38 V

  • -0.19 V


76.

The number of electrons required to reduce 4.5 × 10-5 of Al is

  • 1.03 × 1018

  • 3.01 × 1018

  • 4.95 × 1026

  • 7.31 × 1020


77.

The standard reduction potentials at 298 K for the following half-cell reactions are given on next page

                    Zn2(aq)+ 2e-  Zn(s)-0.762Cr3+(aq)+ 3e- Cr(s)-0.742H+(aq)+ 2e- H2(g)+0.00Fe3+(aq)+ e- Fe2+(aq) +0.77

Which one of the following is the strongest reducing agent?

  • Zn(s)

  • Cr(s)

  • H2(s)

  • Fe2+(aq)


78.

1 C electricity deposits

  • 10.8 g of Ag

  • 96500 g of Ag

  • electrochemical equivalent of Ag

  • half of electrochemical equivalent of Ag


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79.

Given, for Sn4+/ Sn2+, standard reductiona potential is 0.15 V and for Au3+/ Au, standard reduction potential is 1.5 V.

For the reaction,

3Sn2+ + 2Au3+ → 3Sn4+ + 2Au

the value of Ecell° is

  • +1.35

  • +2.55

  • -1.35

  • -2.55


80.

The isotope tha causes skin disease is

  • I131

  • S35

  • P31

  • None of these


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