Which of the following are redox changes?
$(i)$ Hydrolysis of $XeF_2$
$(ii)$ Thermal decomposition of $Ag_2CO_3$
$(iii)$ Reaction of $Al$ with $NaOH$
$(iv)$ Hydrolysis of $PCl_5$
$(v)$ Reaction of $NaCl$ with conc. $H_2SO_4$
Correct options are:

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.

Which one of the following compounds does not decolourise an acidified aqueous solution of $KMnO_4$?

Whenever a reaction between an oxidising agent and a reducing agent is carried out,a compound of lower oxidation state is formed if the reducing agent is in excess and a compound of higher oxidation state is formed if the oxidising agent is in excess. Justify this statement giving three illustrations.

Which of the following statements is incorrect for the auto-ionization reaction of ammonia?
$2NH_3 \rightleftharpoons NH_4^+ + NH_2^-$

Acidified $KMnO_4$ can be decolourised by