What is the oxidation state of chromium in the final product when $KI$ reacts with acidified potassium dichromate solution?

Assign $A, B, C, D$ from the given type of reaction:
$2FeCl_3 + 3KI \longrightarrow 2FeCl_2 + I_2 + 2KCl$
$I_2 + KI \longrightarrow KI_3$
Identify the observation for the product $KI_3$ in the reaction $FeCl_3 + KI \longrightarrow Fe^{2+}(aq.) + KI_3$.

$A$ solution of $KMnO_{4}$ on reduction yields either a colourless solution,a brown precipitate,or a green solution depending on the $pH$ of the solution. What different stages of the reduction do these represent and how are they carried out?

Assign $A, B, C, D$ from the given type of reaction.
$2KI + HgI_2 \downarrow \longrightarrow K_2[HgI_4]$

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

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