In chemical reaction of potassium ferrocyanide and hydrogen peroxide in the presence of dil. ${\mathrm{H}}_2\mathrm{S}{\mathrm{O}}_4$

Complete the following reaction:

$2{\mathrm{FeSO}}_4 \stackrel{∆}{\to } {\mathrm{Fe}}_2{\mathrm{O}}_3 +$_____$+{\mathrm{SO}}_3$

$\mathrm{A}: {\mathrm{Fe}}_3{\mathrm{O}}_4$     $\mathrm{B}: {\mathrm{CO}}_2$     $\mathrm{C}: {\mathrm{SO}}_2$

Enter your correct answer as $\mathrm{A}$, $\mathrm{B}$, or $\mathrm{C}$.

Represent the union of two sets by Venn diagram for each of the following.

$X=\{x | x$ is a prime number between $80$ and $100\}$

$Y=\{y | y$ is an odd number between $90$ and $100\}$

Choosing the substances from the list given below, write the balanced chemical equations for the reactions which would be used in the laboratory to obtain the following salts.

Iron(II) sulphate

Explain the following observation:

Addition of iron to aqueous copper $\left(\mathrm{I}\mathrm{I}\right)$sulphate solution results in a colour change from blue to green.

Write the balanced chemical equation for the preparation of Iron $\left(\mathrm{II}\right)$ sulphate.

An inorganic compound on strong heating gives a black-brown powder and two oxides of sulphur. The powder was dissolved in $\mathrm{HCl}$ when a yellow solution was obtained which gave a blood-red coloured solution with thiocyanide ions. Then, the inorganic compound will be

Which series of reactions correctly represent chemical relations related to iron and its compound?