Upon the addition of a solution $A$ to a strongly acidified solution of barium nitrate,a white precipitate was obtained which did not dissolve even after large addition of water. Solution $A$ contained

Bromine water reacts with $SO_2$ to form

Which of the following processes does not involve oxidation of iron?

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.

$KMnO_4$ reacts with ferrous ammonium sulphate according to the equation
$MnO_4^- + 5Fe^{2+} + 8H^+ \to Mn^{2+} + 5Fe^{3+} + 4H_2O$
Here $10 \ mL$ of $0.1 \ M$ $KMnO_4$ is equivalent to:

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.