Question

Read the following paragraph and answer the questions given below: 

Carbon compounds contain many elements. The element hydrogen is present to a smaller or larger extent in majority of carbon compounds. The compounds which contain carbon and hydrogen as the only two elements are called hydrocarbons. Hydrocarbons are the simplest and the fundamental organic compounds. The smallest hydrocarbon is methane (CH4), formed by combination of one carbon atom and four hydrogen atoms. We have already seen the structure of methane. Ethane is one more hydrocarbon. Its molecular formula is C2H6. The carbon compounds having a double bond or triple bond between two carbon atoms are called unsaturated compounds. Ethene and ethyne are unsaturated hydrocarbons. The unsaturated hydrocarbons containing a carbon-carbon double bond are called ‘Alkenes’. The unsaturated hydrocarbons whose structures contain a carbon-carbon triple bond are called ‘Alkynes’. Generally the unsaturated compounds are more reactive than the saturated compounds.

1. What is meant by hydrocarbon?   (1)
2. Name the smallest hydrocarbon.   (1)
3. Define unsaturated compound.   (1) 
4. Differentiate between Alkene and Alkyne.   (2)

Answer 1

1. Hydrocarbons are compounds that exclusively include the atoms carbon and hydrogen.
2. Among hydrocarbons, methane (CH₄) is the smallest.
3. Unsaturated compounds are carbon compounds with two carbon atoms joined by a double or triple bond.
4. 
   

   	Alkene	Alkyne
   (i)	Alkenes are unsaturated hydrocarbons with double carbon bonds.	Alkynes are unsaturated hydrocarbons that have a triple bond between carbons.
   (ii)	Alkenes have the generic formula CnH2n.	Alkenes have the generic formula CnH2n−2.