In the following reaction mixtures,
$I$. $Cu / CuSO_4 + Ag / Ag_2SO_4$
$II$. $Zn / ZnSO_4 + Cu / CuSO_4$
copper respectively undergoes

Assign $A, B, C, D$ from the given type of reaction.
$NO + NO_2 \xrightarrow{-11 \ ^{\circ}C} N_2O_3$

Which of the following reactions is not feasible?

Given below are two statements :-
Statement $I$ :- In redox titration,the indicators used are sensitive to change in $pH$ of the solution.
Statement $II$ :- In acid-base titration,the indicators used are sensitive to change in oxidation potential.
In the light of the above statements,choose the most appropriate answer from the options given below.

What is the equivalent weight of potassium permanganate $(KMnO_4)$ when it acts as an oxidizing agent in the conversion of ferrous ions to ferric ions in an acidic medium?

In basic medium,$CrO_{4}^{2-}$ oxidises $S_{2}O_{3}^{2-}$ to form $SO_{4}^{2-}$ and itself changes into $Cr(OH)_{4}^{-}$. The volume of $0.154 \ M \ CrO_{4}^{2-}$ required to react with $40 \ mL$ of $0.25 \ M \ S_{2}O_{3}^{2-}$ is ........... $mL$ (Rounded-off to the nearest integer).