What are hydrocarbons? Explain with examples. (b) Explain the meaning of saturated and unsaturated hydrocarbons with two examples each. (c) Give the names and structural formulae of one saturated cyclic hydrocarbon and one unsaturated cyclic hydrocarbon. (d) Give one example of a hydrocarbon, other than pentane, having more than three isomers. (e) How many isomers of the following hydrocarbons are possible? (i) C3H8 (ii) C4H10 (iii) C5H12 (iv) C6H14

• A compound made up of hydrogen and carbon only is called a hydrocarbon. For example: methane (CH4), ethane (C2H6), ethene (C2H4), and ethyne (C2H2), all are hydrocarbons as they are made up of only two elements: carbon and hydrogen.
• Saturated hydrocarbons are those which the carbon atoms are connected by single bonds and also called alkanes. Example: Methane and ethane

Unsaturated hydrocarbons are those which the two carbon atoms are connected by a double bond or a triple bond.

Example: Ethene and ethyne

• Saturated cyclic hydrocarbon: Cyclohexane C6H12 Unsaturated Cyclic hydrocarbon: Benzene C6H6
• Hexane C6H14
• (i) No isomers
• Two
• Three
• Five