Consider the following half-cell reaction: $Cr_2O_7^{2-}{_{\text{(aq)}}} + 14H^{+}{_{\text{(aq)}}} + 6e^{-} \rightarrow 2Cr^{3+}{_{\text{(aq)}}} + 7H_2O_{\text{(l)}}$. The reaction was conducted with the ratio $\frac{[Cr^{3+}]^2}{[Cr_2O_7^{2-}]} = 10^{-6}$. The $pH$ value at which the $EMF$ of the half-cell will become zero is $............$ (nearest integer value). [Given: standard half-cell reduction potential $E^{o}_{Cr_2O_7^{2-}, H^{+} / Cr^{3+}} = 1.33 \ V$,$\frac{2.303 RT}{F} = 0.059 \ V$]

  • A
    $10$
  • B
    $20$
  • C
    $30$
  • D
    $40$

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The Nernst equation is given by $E = E^o - \frac{RT}{nF} \ln Q$. If $Q = K_{eq}$,then which of the following is not correct?

If $E_{cell} = 0.118 \, V$ for the following reaction,calculate $[H^{+}]$ and $pH$ at $298 \, K$ temperature.
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For the cell reaction,$Cu | Cu^{2+}(0.1 \ M) || Cu^{2+}(1.0 \ M) | Cu$,the emf of the cell at $25^{\circ}C$ is given that $E^{\circ}_{Cu^{2+}/Cu} = 0.34 \ V$. (in $V$)

$E_{1}, E_{2}, E_{3}$ are the $EMF$ values of three galvanic cells with the reaction $Zn(s) + Cu^{2+}(aq) \rightarrow Zn^{2+}(aq) + Cu(s)$ at $298 \ K$ with different concentrations: $(I) [Zn^{2+}] = 1 \ M, [Cu^{2+}] = 0.1 \ M$; $(II) [Zn^{2+}] = 1 \ M, [Cu^{2+}] = 1 \ M$; $(III) [Zn^{2+}] = 0.1 \ M, [Cu^{2+}] = 1 \ M$. Compare the $EMF$ values.

The standard $EMF$ for the given cell reaction $Zn + Cu^{2+} \rightarrow Cu + Zn^{2+}$ is $1.10 \ V$ at $25^oC$. The $EMF$ for the cell reaction,when $0.1 \ M \ Cu^{2+}$ and $0.1 \ M \ Zn^{2+}$ solutions are used,at $25^oC$ is .......... $V$.

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