Assign $A, B, C, D$ from the given type of reaction:
$2AgNO_3 + 2NaOH \longrightarrow Ag_2O \downarrow + 2NaNO_3 + H_2O$

$KI$ is oxidised into $I_2$ by using the reagent

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.

Aqueous sulphite reacts with dilute sulphuric acid to form $X_{(g)}$. The liberated $X_{(g)}$ is passed into acidified $KMnO_4$ solution. What is the oxidation state of $Mn$ in the product formed?

The oxidation state of copper changes when aqueous copper $(II)$ ions react with
$(I)$ $NaOH_{(aq)}$
$(II)$ $Fe_{(s)}$
$(III)$ $KI_{(aq)}$

When copper is added to concentrated $H_2SO_4$,$CuSO_4$ is produced along with another sulphur-containing compound $X$. The compound $X$ is