Question

Action of dilute hydrochloric acid on iron(II) sulphide.

Answer 1

We have to know that the hydrochloric acid can be in diluted or concentrated form. It can be found in two forms: gas or liquid. Physical properties such as boiling point, melting point, pH depend upon the concentration of hydrochloric acid. This acid is considered to be a strong acid having ph value lower than $7$.

Complete answer:
We have to know that the Iron(II) this indicates that iron is in $+ 2$ oxidation state. Iron has several oxidation states thus the one with $+ 2$ oxidation state is known as Ferric ion and iron with $+ 1$ oxidation state is known as ferrous ion. When iron (II) sulphide reacts with hydrochloric acid it will lead to the formation of ferric chloride and hydrogen sulphide gas. The hydrogen sulphide gas is a very irritating pungent odor, also indicating a rotten egg like smell. When we follow this chemical reaction bubbling of gas is observed as the hydrogen gas is being escaped from the chamber and also there is formation of a thin ferric chloride layer. The reaction between ferric sulphide and hydrochloric acid can come under the category of replacement reactions. The reaction is represented below:
$FeS + 2HCl \to {\text{ }}FeC{l_2} + {H_2}S$
Since iron and sulphide ions both carry $+ 2$ charge thus valency gets neglected and we get the product as $FeS$ .

Note:
We have to know that the replacement reaction is the one in which atoms in a chemical reaction are being exchanged with each other. Also it can be called a double displacement reaction as the atoms for both the reactants are getting exchanged to new products. Hydrogen sulphide is in gaseous form while ferric chloride is in solid form.