CBSE Class 10 Science 2022 · Paper 31/6/1 · Question 9(a)

(i) (I) The heteroatom is oxygen, O. (II) The functional group is $-\text{OH}$, the alcohol group; the compound is ethanol, ${\text{C}}_2{\text{H}}_5\text{OH}$. (ii) Butane is ${\text{CH}}_3-{\text{CH}}_2-{\text{CH}}_2-{\text{CH}}_3$: four carbon atoms in a chain joined by single bonds, the two end carbons carrying three hydrogens each and the two middle carbons two each (drawn in full in the figure). (iii) (I) Cyclohexane, ${\text{C}}_6{\text{H}}_{12}$: a ring of six carbon atoms joined by single bonds, each carbon bonded to two hydrogens. (II) Benzene, ${\text{C}}_6{\text{H}}_6$: a ring of six carbon atoms, each bonded to one hydrogen, with alternate single and double bonds. Benzene is the unsaturated one.