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Nernst Equation

The standard ...

Question

The standard reduction potentials of $Z n^{2 +} | Z n$ and $C u^{2 +} | C u$ are -0.76V and +0.34V respectively. What is the cell EMF of the following cell?

$Z n | Z n^{2 +} (0.05 M) | | C u^{2 +} (0.005 M) | C u$

[ $\frac{R T}{F} = 0.059$ ]

1.1295 V

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1.0705 V

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1.1000 V

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1.0412 V

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Solution

The correct option is B 1.0705 V
The standard EMF of the given cell is: $E_{c e l l}^{0} = E_{C u^{2 +} | C u}^{0} - E_{Z n^{2 +} | Z n}^{0} = 0.34 V - (- 0.76 V) = 1.1 V$ .
The EMF of cell is: $E_{c e l l} = E_{c e l l}^{0} - \frac{0.059}{n} l o g \frac{[Z n^{2 +}]}{[C u^{2 +}]}$ .
$E_{c e l l} = 1.1 V - \frac{0.059}{2} l o g \frac{0.05}{0.005} = 1.1 V - 0.0295 V = 1.0705 V$ .

Hence, option B is correct.

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Similar questions

The standard reducation potentials of

$Z n^{2 +} | Z n, C u^{2 +} | C u$ and $A g^{+} | A g$

are respectively -0.76, 0.34 and 0.8 V. The following cells were constructed.

a) $Z n | Z n^{2 +} | | C u^{2 +} | C u$

b) $Z n | Z n^{2 +} | | A g^{+} | A g$

c) $C u | C u^{2 +} | | A g^{+} | A g$

What is the correct order $E {^{0}}_{c e l l}$ of these cells?

Z n | Z n^{2 +} (a q) (1.0 M) | | C u^{2 +} (a q) (1.0 M) | | C u

0.350

C u^{2 +} (a q) + 2 e^{-} \to C u

- 0.763

Z n^{2 +} (a q) + 2 e^{-} \to Z n

Z n | Z n^{2 +} (0.001 M) | | C u^{2 +} (0.1 M) | C u

C u / C u^{2 +}

Z n / Z n^{2 +}

Z n | Z n^{2 +} (a q) (1.0 M) | | C u^{2 +} (a q) (1.0 M) | | C u

C u^{2 +} (a q) + 2 e^{-} \to C u

Z n^{2 +} (a q) + 2 e^{-} \to Z n

Z n ∣ ∣ {Z n}^{2 +} (1 M) ∣ ∣ ∣ ∣ {C u}^{2 +} (1 M) ∣ ∣ C u

E_{{C u}^{2 +} / C u}^{o} = 0.34 V

E_{{z n}^{2 +} / Z n}^{o} = - 0.76 V

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