Assign $A, B, C, D$ from the given type of reaction.
$KI + BiI_3 \downarrow \longrightarrow K[BiI_4]$

Assign $A, B, C, D$ for the given type of reaction:
$Mn(NO_3)_2 + 2NaOH \longrightarrow Mn(OH)_2 \downarrow + 2NaNO_3$

In order to oxidize a mixture of one mole of each of $FeC_2O_4$,$Fe_2(C_2O_4)_3$,$FeSO_4$ and $Fe_2(SO_4)_3$ in acidic medium,the number of moles of $KMnO_4$ required is

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.

$A$ sample $(5.6 \ g)$ containing iron is completely dissolved in cold dilute $HCl$ to prepare $250 \ mL$ of solution. Titration of $25.0 \ mL$ of this solution requires $12.5 \ mL$ of $0.03 \ M \ KMnO_4$ solution to reach the end point. The number of moles of $Fe^{2+}$ present in the $250 \ mL$ solution is $x \times 10^{-2}$ (consider complete dissolution of $FeCl_2$). The amount of iron present in the sample is $y \%$ by weight. (Assume: $KMnO_4$ reacts only with $Fe^{2+}$ in the solution. Use: Molar mass of iron as $56 \ g \ mol^{-1}$)
$(1)$ The value of $x$ is. . . . .
$(2)$ The value of $y$ is. . . . .

One litre of $0.15 \ M \ Na_2SO_3$ aqueous solution is mixed with $500 \ mL$ of $0.2 \ M \ K_2Cr_2O_7$ aqueous solution in acid medium. What is the concentration (in $mol \ L^{-1}$) of unreacted $K_2Cr_2O_7$ in the resultant solution?