Question

Oxidation number of $C$ in $HCN$ is _____________
A: +2
B: -3
C: +3
D: zero

Answer 1

Hint: Oxidation number of an atom is the charge that an atom will possess if the compound was ionic. Ionic compounds are compounds made up of ions. These ions are atoms that gain or lose electrons, giving them a net positive or negative charge.

Complete step by step answer:
As we know $HCN$ is Hydrogen cyanide. It is a linear triatomic molecule in which there is a triple bond between $C$ and $N$ ,and a single bond between $H$ and $C$.
In Hydrogen Cyanide $HCN$ , Let oxidation number of $C$ be $x$
We know that oxidation no. of nitrogen =$- 3$ and that of Hydrogen =$+ 1$
We know that as a whole compound is neutral, i.e. total charge on compound is zero
So on equating we will get $x + 1 - 3 = 0$
$x = + 2$
Therefore the oxidation number of $C$ in $HCN$ is $2$ . So, the answer to this question is option A i.e. $+ 2$ .
Additional Information: Oxidation number is also called an oxidation state. Which is the total number of electrons that an atom either gains or loses to form bonds with other atoms. If an oxidation state is positive that means the atom acquires electrons in a chemical reaction or a negative oxidation state means the atom donates an electron in a chemical reaction. Each after that participates in a chemical reaction is assigned an oxidation state. In nomenclature of inorganic chemistry, the oxidation state of an element that has ability to exist in more than one oxidation state is indicated by Roman numeral in parentheses after the name of the element.
Properties of hydrogen cyanide: It is a hydracid it is a conjugate acid of cyanide it is a tautomer of hydrogen cyanide.
Tautomers are isomers of a compound which differ only in the position of protons and electrons; a reaction which involves simple proton transfer in an intramolecular fashion is called a tautomerism. Keto enol tautomerism is a very common process and is acid or base catalyzed.
Hydrogen cyanide is a very important compound used for making compounds ranging from polymers to plastics. It is used in the pharmaceuticals industry and also for fumigation of ships and buildings.

Note: Hydrogen isocyanide is a tautomeric form of Hydrogen cyanide that means they differ only in structure. Hydrogen isocyanide has been proposed as an important intermediate in oxidation of hydrogen cyanide. Hydrogen cyanide is also called prussic acid.