$A$ battery is constructed of $Cr$ and $Na_2Cr_2O_7$. The unbalanced chemical equation when such a battery discharges is: $Na_2Cr_2O_7 + Cr + H^{+} \to Cr^{3+} + H_2O + Na^{+}$. If one Faraday of electricity is passed through the battery during charging,the number of moles of $Cr^{3+}$ removed from the solution is:

Solutions $A$,$B$,and $C$ of the same strong electrolyte offered resistances of $50 \ \Omega$,$100 \ \Omega$,and $150 \ \Omega$ in a given conductivity cell. The resistance observed if they are mixed in a volume proportion which is the reciprocal of their resistances and tested in the same conductivity cell would be ............. $\Omega$.

Match List-$I$ with List-$II$.

List-$I$ (Conversion)	List-$II$ (Number of Faraday required)
$A$. $1 \ mol$ of $H_2O$ to $O_2$	$I$. $3 \ F$
$B$. $1 \ mol$ of $MnO_4^{-}$ to $Mn^{2+}$	$II$. $2 \ F$
$C$. $1.5 \ mol$ of $Ca$ from molten $CaCl_2$	$III$. $1 \ F$
$D$. $1 \ mol$ of $FeO$ to $Fe_2O_3$	$IV$. $5 \ F$

Choose the correct answer from the options given below:

Given that $E^o_{Fe^{2+}/Fe} = -0.44 \ V$,$E^o_{Cu^{2+}/Cu} = 0.34 \ V$,and $E^o_{Ag^+/Ag} = 0.80 \ V$. Which of the following statements is correct?

Using the standard electrode potentials given in the Table $8.1$,predict if the reaction between the following is feasible:
$(a)$ $Fe^{3+}_{(aq)}$ and $I^{-}_{(aq)}$
$(b)$ $Ag^{+}_{(aq)}$ and $Cu_{(s)}$
$(c)$ $Fe^{3+}_{(aq)}$ and $Cu_{(s)}$
$(d)$ $Ag_{(s)}$ and $Fe^{3+}_{(aq)}$
$(e)$ $Br_{2(aq)}$ and $Fe^{2+}_{(aq)}$

Consider the following electrochemical cell at standard condition: $Au_{(s)} | QH_2, Q | NH_4X(0.01 \ M) || Ag^{+}(1 \ M) | Ag_{(s)}$. Given $E_{\text{cell}} = +0.4 \ V$. The couple $QH_2 / Q$ represents the quinhydrone electrode,and the half-cell reaction is given as: $Q + 2e^- + 2H^+ \rightarrow QH_2$ with $E^o_{Q/QH_2} = +0.7 \ V$. Given: $E^o_{Ag^+/Ag} = +0.8 \ V$ and $\frac{2.303 \ RT}{F} = 0.06 \ V$. The $pK_b$ value of the ammonium halide salt $(NH_4X)$ used here is $.........$ (nearest integer).