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Nernst Equation

Calculate the...

Question

Calculate the potential of a half cell having reaction: $A g_{2} S (s) + 2 e^{-} ⇌ 2 A g (s) + S^{2 -} (a q)$ in a solution buffered at $p H = 3$ and which is also saturated with $0.1 M H_{2} S (a q) :$
[Given: $K_{s p} (A g_{2} S) = 10^{- 49}, K_{a_{1}} . K_{a_{2}} = 10^{- 21}$ ]

1.18

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0.19

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- 0.19 V

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Solution

The correct option is D $- 0.19 V$
Nernst equation:
$E = E^{0} - 2.303 R T l o g Q / n F$
And for $H_{2} S$

$K = \frac{[H^{+}]^{2} [S^{- 2}]}{[H_{2} S]}; 10^{- 21}$ = $\frac{[10^{- 3}]^{2} [S^{- 2}]}{[0.1]}; [S^{- 2}] = 10^{- 16}$

$E = E^{0} - 2.303 R T l o g Q / n F = 0 - (0.066 / 2) l o g [S^{- 2}] = - 0.19 V$

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Similar questions

A g_{2} S + 2 e^{-} \to 2 A g + S^{2 -}

H_{2} S

H_{2} S : K_{1} = 10^{- 8}

K_{2} = 2 \times 10^{- 13}, K_{s p} (A g_{2} S) = 2 \times 10^{- 48}, E_{A g^{+} | A g}^{0} = 0.8 V

A g_{2} S (s) + 2 e^{-} \to 3 A g (s) + S^{2 -}

P t_{A g_{2} S | A g, H_{2} S (0.1 M)} a t [H^{\oplus}] = 10^{- 3},

[E_{A g^{\oplus} | A g}^{⊖} = 0.80 V, K_{a (H_{2} S)} = 10^{- 21}, a n d K_{s p} o f A g_{2} S = 10^{- 49}]

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