Question

Strong heating of ferrous sulphate leads to the formation of a brown solid and two gases. This reaction can be categorised as

• A. displacement and redox.
• B. decomposition and redox
• C. displacement and endothermic
• D. decomposition and exothermic

Answer 1

The correct option is B

decomposition and redox

Explanation for correct option:

Option (B) decomposition and redox:

Heating of Ferrous sulphate$\mathbf{\left(}{\mathbf{FeSO}}_{\mathbf{4}}\mathbf{\right)}$:-

• Decomposition reaction is a type of reaction where a compound is broken done into two or more compounds.
• On the other hand redox reaction is a type of reaction where both oxidation and reduction occur.
• Here it is given that Ferrous sulphate$\left({\mathrm{FeSO}}_4\right)$ is being heated, and a brown solid of Ferric oxide$\left({\mathrm{Fe}}_2{\mathrm{O}}_3\right)$ and two gases Sulphur dioxide$\left({\mathrm{SO}}_2\right)$ and Sulphur trioxide$\left({\mathrm{SO}}_3\right)$ are formed.
• The complete balanced reaction is:

$\underset{\mathrm{Ferrous}\mathrm{sulphate}}{2{\mathrm{FeSO}}_4\left(\mathrm{s}\right)}\to \underset{\mathrm{Ferric}\mathrm{oxide}}{{\mathrm{Fe}}_2{\mathrm{O}}_3\left(\mathrm{s}\right)}+\underset{\mathrm{Sulphur}\mathrm{dioxide}}{{\mathrm{SO}}_2\left(\mathrm{g}\right)}+\underset{\mathrm{Sulphur}\mathrm{trioxide}}{{\mathrm{SO}}_3\left(\mathrm{g}\right)}$

• Here we can clearly see that Ferrous sulphate$\left({\mathrm{FeSO}}_4\right)$ decomposes into Ferric oxide$\left({\mathrm{Fe}}_2{\mathrm{O}}_3\right)$, Sulphur dioxide$\left({\mathrm{SO}}_2\right)$ and Sulphur trioxide$\left({\mathrm{SO}}_3\right)$.
• Hence we can call it a decomposition reaction.

Redox reaction of Ferrous sulphate$\mathbf{\left(}{\mathbf{FeSO}}_{\mathbf{4}}\mathbf{\right)}$:-

• The oxidation number of Iron in Ferrous sulphate is $+2$, which gets changed to $+3$in Ferric oxide after being heated.
• That is Iron is getting oxidised here.
• On the other hand oxidation number of Sulphur in Ferric sulphate is$+6$, which gets changed to $+4$in Sulphur dioxide.
• That is Sulphur is getting reduced here.
• The reaction is given like:

$\underset{\mathrm{Ferrous}\mathrm{sulphate}}{\stackrel{+2}{2\mathrm{F}}\mathrm{e}\stackrel{+6}{\mathrm{S}}{\mathrm{O}}_4\left(\mathrm{s}\right)}\to \underset{\mathrm{Ferric}\mathrm{oxide}}{{\stackrel{+3}{\mathrm{Fe}}}_2{\mathrm{O}}_3\left(\mathrm{s}\right)}+\underset{\mathrm{Sulphur}\mathrm{dioxide}}{\stackrel{+4}{\mathrm{S}}{\mathrm{O}}_2\left(\mathrm{g}\right)}+\underset{\mathrm{Sulphur}\mathrm{trioxide}}{{\mathrm{SO}}_3\left(\mathrm{g}\right)}$

• Thus it is also a redox reaction, as both oxidation and reduction take place in the same reaction.
• Hence it is the correct option.

Therefore, Strong heating of ferrous sulphate leads to the formation of a brown solid and two gases. This reaction can be categorised as option (B) decomposition and redox