Question

(a)- Write the dehydrating reaction of ethanol and write the name of dehydrating agent.
(b)- Choose correct series for the following:

Compound	Series
(i)- Ethane	(a)- Unsaturated hydrocarbon
(ii)- Benzene	(b)- Long chain saturated hydrocarbon
(iii)- Hexane	(c)- Hydrocarbon having odd atom
(iv)- Methyl alcohol	(d)- Saturated hydrocarbon

Answer 1

Dehydrating reaction means there will be elimination of a water molecule, and ethanol is an alcohol molecule, so when there is removal of water molecule, an alkene is formed. Unsaturated hydrocarbon means when the chain of the hydrocarbon contains either a double bond or a triple bond, and saturated hydrocarbons are those which have only single bonds.

Complete step by step answer:
(a)- Dehydrating reaction means there will be elimination of a water molecule, and ethanol is an alcohol molecule, so when there is removal of water molecule, an alkene is formed. Ethanol is a compound in which there are two carbon atoms and there is one alcohol functional group. When the ethanol is treated with concentrated sulfuric acid then there is formation of ethene by dehydration. The reaction is given below:
$C{{H}_{3}}C{{H}_{2}}OH\xrightarrow{{{H}_{2}}S{{O}_{4}}}C{{H}_{2}}=C{{H}_{2}}+{{H}_{2}}O$

(b)- (i)- Ethane is a hydrocarbon in which there are two carbon atoms and this compound only has single bonds, so it will be a saturated hydrocarbon.
(ii)- Benzene is a hydrocarbon in which there are six carbon atoms and these carbon atoms form a ring structure, and there are three double bonds in benzene, so this is an unsaturated hydrocarbon.
(iii)- Hexane is a hydrocarbon in which there are six carbon atoms and this compound has only single bonds, so it will be a long chain saturated hydrocarbon.
(iv)- Methyl alcohol is a hydrocarbon in which there is only one carbon atom and one is an odd number and it has a alcohol functional group, so it is a hydrocarbon having odd atoms.
The series will be: (i)- (d), (ii)- (a), (iii)- (b), (iv)- (c).

Note: Some example of unsaturated hydrocarbon having double bonds are ethene having formula $C{{H}_{2}}=C{{H}_{2}}$, butene having formula $C{{H}_{3}}-C{{H}_{2}}-CH=C{{H}_{2}}$, and some examples of unsaturated hydrocarbon having triple bonds and ethyne having formula $CH\equiv CH$, propyne having formula $C{{H}_{3}}-C\equiv CH$, etc.