CBSE Class 10 Science 2017 · Paper 31/2/3 · Question 8

Hydrocarbons are compounds of carbon and hydrogen only. (i) Saturated (open-chain) hydrocarbons, the alkanes: ${\text{C}}_n{\text{H}}_{2n+2}$. Example: ethane, ${\text{C}}_2{\text{H}}_6$, ${\text{CH}}_3-{\text{CH}}_3$, with single bonds only (structure in the figure). (ii) Unsaturated hydrocarbons: alkenes, with one carbon–carbon double bond, ${\text{C}}_n{\text{H}}_{2n}$; alkynes, with one carbon–carbon triple bond, ${\text{C}}_n{\text{H}}_{2n-2}$. Example: ethene, ${\text{C}}_2{\text{H}}_4$, ${\text{CH}}_2={\text{CH}}_2$ (structure in the figure).