Which of the following of metals- when coupled- will give maximum EMF for a voltaic cell-Given-Au-aq - e- - Aus- E0 - 1-69 VCu2-aq - 2e- - Cus- E0 - 0-34 VPb2-aq - 2e- - Pbs- E0 - -0-13 VFe2-aq - 2e- - Fes- E0 -0-44 VCa2-aq - 2e- - Cas- E0 - -2-87 V

Standard reduction potentials (SRP) of the half cell electrodes are calculated and arranged nbsp;in nbsp;a series of increasing order which is known as elec ...

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Standard XII

Chemistry

Redox Reactions

Which of the ...

Question

Which of the following of metals, when coupled, will give maximum EMF for a voltaic cell?
Given:
$A u^{+} (a q) + e^{-} \to A u (s); E^{0} = 1.69 V$
$C u^{2 +} (a q) + 2 e^{-} \to C u (s); E^{0} = 0.34 V$
$P b^{2 +} (a q) + 2 e^{-} \to P b (s); E^{0} = - 0.13 V$
$F e^{2 +} (a q) + 2 e^{-} \to F e (s); E^{0} = - 0.44 V$
$C a^{2 +} (a q) + 2 e^{-} \to C a (s); E^{0} = - 2.87 V$

F e and A u

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P b and A u

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C u and A u

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C a and C u

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Solution

The correct option is D $C a and C u$
Standard reduction potentials (SRP) of the half cell electrodes are calculated and arranged in a series of increasing order which is known as electrochemical series.
The standard electrode potential of $H^{+} / H_{2}$ couple is zero.

Here, a negative $E^{0}$ signifies that it has high tendency to get oxidised and the redox couple is a stronger reducing agent than the $H^{+} / H_{2}$ couple.

A positive $E^{0}$ signifies that it has high tendency to get reduced and the redox couple is a stronger oxidising agent than the $H^{+} / H_{2}$ couple.

Electrochemical series helps in the selection of electrode assemblies to construct the galvanic cells of desired EMFs.

For a galvanic cell to provide high cell voltage, the half cell having higher reduction potential and lower reduction potential should be coupled.

In given electrochemical series,
$A u^{+} (a q) + e^{-} \to A u (s) (Highest value)$
$C a^{2 +} (a q) + 2 e^{-} \to C a (s) (Lowest value)$

$E_{c e l l}^{0} = SRP of substance reduced - SRP of substance oxidised$
(SRP - Standard reduction potential)

$E_{c e l l}^{0} = E_{c a t h o d e (r e d)}^{0} - E_{a n o d e (r e d)}^{0}$

For (a),
$E_{c e l l}^{0} = 1.69 - (- 0.44)$
$E_{c e l l}^{0} = 2.13 V$

For (b),
$E_{c e l l}^{0} = 1.69 - (- 0.13)$
$E_{c e l l}^{0} = 1.82 V$

For (c),
$E_{c e l l}^{0} = 1.69 - 0.34$
$E_{c e l l}^{0} = 1.35 V$

For (d),
$E_{c e l l}^{0} = 0.34 - (- 2.87)$
$E_{c e l l}^{0} = 3.21 V$

Thus, the SRP difference will be maximum for $C a$ and $C u$ .
Hence, it gives the maximum EMF for a voltaic cell.

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Similar questions

Q. Which of the following metals, when coupled, will leads to a non-spontaneous cell reaction?
Given:

A u^{+} (a q) + e^{-} \to A u (s); E^{0} = 1.69 V

C u^{2 +} (a q) + 2 e^{-} \to C u (s); E^{0} = 0.34 V

P b^{2 +} (a q) + 2 e^{-} \to P b (s); E^{0} = - 0.13 V

F e^{2 +} (a q) + 2 e^{-} \to F e (s); E^{0} = - 0.44 V

C a^{2 +} (a q) + 2 e^{-} \to C a (s); E^{0} = - 2.87 V

Q. Which of the following metals will couple to provide a higher cell potential for a galvanic cell?

Z n^{2 +} (a q) + 2 e^{-} \to Z n (s); E^{0} = - 0.76 V

C u^{2 +} (a q) + 2 e^{-} \to C u (s); E^{0} = 0.34 V

N i^{2 +} (a q) + 2 e^{-} \to N i (s); E^{0} = - 0.25 V

P b^{2 +} (a q) + 2 e^{-} \to P b (s); E^{0} = - 0.13 V

F e^{2 +} (a q) + 2 e^{-} \to F e (s); E^{0} = - 0.44 V

Q. Which of the following reaction will provide maximum voltage?
Given:

Z n^{2 +} (a q) + 2 e^{-} \to Z n (s); E^{0} = - 0.76 V

C u^{2 +} (a q) + 2 e^{-} \to C u (s); E^{0} = 0.34 V

A g^{+} (a q) + e^{-} \to A g (s); E^{0} = 0.80 V

2 H^{+} (a q) + 2 e^{-} \to H_{2} (g); E^{0} = 0 V

N i^{2 +} (a q) + 2 e^{-} \to N i (s); E^{0} = - 0.25 V

Q. For

M^{2 +} / M and M^{3 +} / M^{2 +}

systems,

E^{0}

values for some metals are as follows:

C r^{2 +} (a q) + 2 e^{-} \to C r (s); E^{0} = - 0.91 V C r^{3 +} (a q) + e^{-} \to C r^{2 +} (a q); E^{0} = - 0.41 V

M n^{2 +} (a q) + 2 e^{-} \to M n (s); E^{0} = - 1.2 V M n^{3 +} (a q) + e^{-} \to M n^{2 +} (a q); E^{0} = + 1.51 V

F e^{2 +} (a q) + 2 e^{-} \to F e (s); E^{0} = - 0.44 V F e^{3 +} (a q) + e^{-} \to F e^{2 +} (a q); E^{0} = + 0.77 V

Which of the following statement(s) is/are correct regarding the given standard reduction potentials?

Q. Which of the following statement(s) is/are true?

M g^{2 +} (a q) + 2 e^{-} \to M g (s); E^{0} = - 2.36 V

C u^{2 +} (a q) + 2 e^{-} \to C u (s); E^{0} = 0.34 V

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Which of the following of metals, when coupled, will give maximum EMF for a voltaic cell? Given: Au+(aq)+e−→Au(s); E0=1.69 V Cu2+(aq)+2e−→Cu(s); E0=0.34 V Pb2+(aq)+2e−→Pb(s); E0=−0.13 V Fe2+(aq)+2e−→Fe(s); E0=−0.44 V Ca2+(aq)+2e−→Ca(s); E0=−2.87 V