Question

Give general formulae of alkanes, alkenes and alkynes.

Answer 1

• General formula of alkanes
• When the number of Hydrogen atoms exceeds the number of Carbon atoms by two, the hydrocarbon is classified as an alkane.
• The number of Hydrogen atoms in an alkane with $\mathrm{n}$ Carbon atoms in its molecule will be $2\mathrm{n}+2$.
• Therefore, the general formula of alkane is ${\mathrm{C}}_{\mathrm{n}}{\mathrm{H}}_{2\mathrm{n}+2}$.
• General formula of alkenes
• When the number of Hydrogen atoms equals the number of Carbon atoms, the hydrocarbon is classified as an alkene.
• The number of Hydrogen atoms in an alkene with $\mathrm{n}$ Carbon atoms in its molecule will be $2\mathrm{n}$.
• Therefore, the general formula of alkene is ${\mathrm{C}}_{\mathrm{n}}{\mathrm{H}}_{2\mathrm{n}}$.
• General formula of alkynes
• The given hydrocarbon is an alkyne if the number of hydrogen atoms is two less than double the number of Carbon atoms. Thus,
• The number of Hydrogen atoms in an alkyne molecule with $\mathrm{n}$ Carbon atoms is $2\mathrm{n}-2$.
• Therefore, the general formula of alkyne is ${\mathrm{C}}_{\mathrm{n}}{\mathrm{H}}_{2\mathrm{n}-2}$.