CBSE Class 10 Science 2018 · Paper 31(B) · Question 3

(i) Alkanes are saturated hydrocarbons, whose carbon atoms are joined by single bonds only; general formula ${\text{C}}_n{\text{H}}_{2n+2}$ (for example ethane, ${\text{C}}_2{\text{H}}_6$). (ii) Alkenes are unsaturated hydrocarbons containing a carbon–carbon double bond; general formula ${\text{C}}_n{\text{H}}_{2n}$ (for example ethene, ${\text{C}}_2{\text{H}}_4$). (iii) Alkynes are unsaturated hydrocarbons containing a carbon–carbon triple bond; general formula ${\text{C}}_n{\text{H}}_{2n-2}$ (for example ethyne, ${\text{C}}_2{\text{H}}_2$). ${\text{C}}_4{\text{H}}_{10}$ is an alkane, butane: with $n=4$, $2n+2=10$.