For the following redox reaction, find the correct statement: $Sn^{2+} + 2Fe^{3+} \rightarrow Sn^{4+} + 2Fe^{2+}$

Assign $A$,$B$,$C$,$D$ from the given type of reaction.
$N_2 + O_2 \xrightarrow{\text{High temp.}} 2NO - \text{Heat}$

$20 \, mL$ of $0.02 \, M \, K_2Cr_2O_7$ solution is used for the titration of $10 \, mL$ of $Fe^{2+}$ solution in the acidic medium. The molarity of $Fe^{2+}$ solution is ........... $\times 10^{-2} \, M$ (Nearest Integer).

Which of the following is oxidised by $SO_2$?

Consider the reactions:
$(a)$ $6 CO_{2(g)} + 6 H_{2}O_{(l)} \rightarrow C_{6}H_{12}O_{6(aq)} + 6 O_{2(g)}$
$(b)$ $O_{3(g)} + H_{2}O_{2(l)} \rightarrow H_{2}O_{(l)} + 2 O_{2(g)}$
Why is it more appropriate to write these reactions as:
$(a)$ $6 CO_{2(g)} + 12 H_{2}O_{(l)} \rightarrow C_{6}H_{12}O_{6(aq)} + 6 H_{2}O_{(l)} + 6 O_{2(g)}$
$(b)$ $O_{3(g)} + H_{2}O_{2(l)} \rightarrow H_{2}O_{(l)} + O_{2(g)} + O_{2(g)}$
Also,suggest a technique to investigate the path of the above $(a)$ and $(b)$ redox reactions.

$X + H_2SO_4 \to Y$ (colorless gas) and $Y + K_2Cr_2O_7 + H_2SO_4 \to$ green solution. Then $X$ and $Y$ are respectively ........