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Equilibrium Constant from Nernst Equation

At equimolar ...

Question

At equimolar concentrations of $F e^{2 +}$ and $F e^{3 +}$ , what must $[A g^{+}]$ be so that the voltage of the galvanic cell made from $A g^{+} / A g$ and $F e^{3 +} / F e^{2 +}$ electrodes equals zero? The reaction is $F e^{2 +} + A g^{+} ⇌ F e^{3 +} + A g$ . Determine the equilibrium constant at $25^{\circ} C$ for the reaction. (Given: $E_{A g^{+} / A g}^{\circ} = 0.799 v o l t$ and $E_{F e^{3 +} / F e^{2 +}}^{\circ} = 0.771 v o l t$ ).

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Solution

$E_{c e l l}^{\circ} = E_{F e^{2 +} / F e^{3 +}}^{\circ} + E_{A g^{+} / A g}^{\circ}$
$= - 0.771 + 0.799 = 0.028 v o l t$
At equilibrium, $E_{c e l l} = 0$
$0 = E_{c e l l}^{\circ} - \frac{0.0591}{1} log \frac{[F e^{3 +}]}{[F e^{2 +}] [A g^{+}]}$
$= E_{c e l l}^{\circ} - 0.0591 log \frac{1}{[A g^{+}]}$
$[A g^{+}] = 0.34$
$log K = \frac{n E^{\circ}}{0.0591}; K = 3.0$ .

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Similar questions

Q. At equimolar concentrations of

F e^{2 +}

F e^{3 +}

A g^{+}

] be so that the voltage of the galvanic cell made from the (

A g^{+} | A g)

F e^{3 +} | F e^{2 +})

electrodes equals zero ?

F e^{2 +} + A g^{+} ⇌ F e^{3 +} + A g

E_{A g^{o} | A g}^{o} = 0.7991; E_{F e^{3 +} | F e^{2 -}}^{o} = 0.771

Q. At equimolar concentration of

F e^{2 +} and F e^{3 +}

[A g^{+}]

be so that the voltage of the galvanic cell made from

(A g^{+} / A g and F e^{3 +} / F e^{2 +})

electrodes equals zero? The reaction is

F e^{2 +} + A g^{+} ⇌ F e^{3 +} + A g

E_{A g^{+} / A g}^{0} = 0.799

E_{F e^{+} / F e^{2 +}}^{0} = 0.771 volt., 10^{- 0.47} = 2.94)

Give your answer upto two decimal only.

Q. A galvanic cell is constructed with

A g^{+} / A g

F e^{3 +} / F e^{2 +}

electrodes. The concentrations of

A g^{+}

at which the e.m.f. of the cell is zero at equimolar concentration of

F e^{2 +}

F e^{3 +}

. Write answer as nearest integer after multiplying it with

10

E_{A g^{+} / A g}^{o} = 0.80 V

E_{F e^{3 +} / F e^{2 +}}^{o} = 0.77 V

E^{\circ}

values to calculate

△ G^{\circ}

for the reaction

F e^{2 +} + A g^{+} \to F e^{3 +} + A g

E_{A g^{+} / A g}^{\circ} = 0.80 v o l t

E_{P t / F e^{3 +}, F e^{2 +}}^{\circ} = 0.77 v o l t

Q. The equilibrium constant at

25^{\circ} C

for the reaction

F e^{2 +} + A g^{+} ⇌ F e^{3 +} + A g

E_{A g^{+} / A g}^{0} = 0.7998 V a n d E_{F e^{3 +} / F e^{2 +}}^{0} = 0.771 V

, log 2 =0.30, log 3 = 0.48,

\frac{2.303 R T}{F} = 0.06

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