Question

Given,$xg$ of $F{e_2}{\left( {S{O_4}} \right)_3}$ was dissolved in water to prepare $1L$ of aqueous solution. Upon analysis it was found that each mL of solution contains $1.2{\text{ }} \times {\text{ }}{10^{ - 4}}$ moles of $S{O_4}^{2 - }$ ions. Find the value of $x$.
A) $16$
B) $124$
C) $31$
D) $64$

Answer 1

We have to know that the ferric sulphate contains two iron ions and three sulphate ions. Ferrous sulfate appears as a greenish or yellow-brown crystalline solid. Melts at $64^\circ C$ and loses the seven waters of hydration at $90^\circ C$. The primary hazard is the threat to the environment. Immediate steps should be taken to limit its spread to the environment.

Complete answer:
We will solve this question step by step;
One mole of ferric sulphate dissociates in water to give three moles of sulphate ions.
Hence, $\dfrac{x}{{400}}$ moles of ferric sulphate present in $1L$ will dissociate to form $\dfrac{{3x}}{{400}}$ moles of sulphate ions.
But it is given that moles of sulphate ions present in $1mL$ is $1.2 \times {10^{ - 4}}$ moles.
We need to find the value of $x$ so,
$\dfrac{{3x}}{{400 \times 1000}} = 1.2 \times {10^{ - 4}}$
On simplification we get,
$x = 16g$
Ferric sulfate is used as a solution generated from iron wastes. The actual speciation is vague but its applications do not demand high purity materials. As such iron (III) sulfate is generated and handled as an aqueous solution. It is produced on a large scale by treating sulfuric acid, a hot solution of ferrous sulfate, and an oxidizing agent. Ferrous sulfate appears as a greenish or yellow-brown crystalline solid. Melts at $64^\circ C$ and loses the seven waters of hydration at $90^\circ C$.

The final answer is D.

Note:
We must have to know that iron sulfates occur as a variety of rare and commercially unimportant minerals. Mikasaite, a mixed iron-aluminum sulfate of chemical formula ${(F{e^{3 + }},A{l^{3 + }})_2}{(S{O_4})_3}$ is the name of mineralogical form of iron (III) sulfate. This anhydrous form occurs very rarely and is connected with coal fires.