Question

When ferrous sulfide reacts with sulfuric acid, the product obtained has a characteristic odor of:
A. urine
B. fishy
C. rotten egg
D. pleasant

Answer 1

Hint: There are many types of chemical reactions like displacement, double displacement reaction, combination reaction, neutralization reaction etc. This reaction is an example of double displacement reaction.

Complete step by step solution:
We can classify displacement reactions as metal-metal displacement reactions and metal-non-metal displacement reactions on the basis of the elements involved in it. It is also classified as single displacement and double displacement reactions.
The given reaction of ferrous sulfide and sulfuric acid is a double displacement reaction. Mutual exchange of ions in two different compounds occur in double displacement reactions. The displacement reaction is based on the reactivity of the elements. The cations are switched. The ions that are in lower positions of electrochemical series will get displaced by the ions which are in higher position. The elements are arranged on the basis of their reduction potentials. Here, iron has more negative value of reduction potential than hydrogen. So iron displaces hydrogen. Thus the complete balanced chemical equation of reaction of ferrous sulfide and sulfuric acid is given below:
${\text{FeS}} + {{\text{H}}_2}{\text{S}}{{\text{O}}_4} \to {\text{FeS}}{{\text{O}}_4} + {{\text{H}}_2}{\text{S}}$
${\text{FeS}} \to $ Ferrous sulfide
${\text{FeS}}{{\text{O}}_4} \to $Ferrous sulfate
${{\text{H}}_2}{\text{S}}{{\text{O}}_4} \to $ Sulfuric acid
${{\text{H}}_2}{\text{S}} \to $ hydrogen sulfide
The products formed are ferrous sulfate and hydrogen sulfide gas. The hydrogen sulfide gas is a toxic or poisonous gas. Since it contains sulfur, it has the smell of rotten eggs.

Hence the correct option is D.

Note: It’s always said that the smell of sulfur is like that of rotten eggs. Thus the sulfur is responsible for the smell of hydrogen sulfide. Unlike sulfur, hydrogen sulfide is clear or transparent, but sulfur is yellow in color. Hydrogen sulfide has a sweetish taste.