Question

An unsaturated hydrocarbon:
A) Contains six carbon atoms
B) Contains fewer hydrogen atoms than is needed for carbon to have its usual valency of four
C) Contains excess hydrogen
D) Contains a chain of the carbon atom

Answer 1

Hint: the unsaturated hydrocarbon is made of carbon and hydrogen, the adjacent carbon atoms are bonded by a double or triple bond. Carbon is tetravalent. It forms four bonds. If the carbons have the double or triple bond and have a fewer number of hydrogen than the saturated hydrocarbons some of the valency is occupied by extra bonds.

Complete step by step answer:
The organic compounds contain carbon and hydrogen and they are called hydrocarbons. Hydrocarbon differs in the type of carbon-carbon bonds. Many hydrocarbons are present in various s household components. The hydrocarbons can be differentiated based on bonding between the carbon atoms. This leads to the difference in the geometries and hybridization of the carbon.
The organic compound which is made up of carbon and hydrogen atoms and consists of a double or triple bond between the adjacent carbon atoms is called the unsaturated hydrocarbons.
The unsaturated hydrocarbons which have at least one double bond between the adjacent carbon atoms are known as the alkene and those which contain the triple bond are called the alkynes.
The unsaturated hydrocarbons are classified as alkenes, alkynes, and aromatic hydrocarbon.
The unsaturated hydrocarbon in which the carbon-carbon atoms consist of the double bond is called the alkene. We know that carbon is tetravalent. It has a valency of 4.Therefore, carbon can form four bonds.in alkene, the$\text{ C-C}$have the two bonds, therefore each carbon can now bond with the two hydrogens. The general formula is \[\text{ }{{\text{C}}_{\text{n}}}{{\text{H}}_{\text{2n}}}\].
$\begin{matrix}
   {} & {} & {} & {} & {} \\
   - & \text{C} & \text{=} & \text{C} & - \\
   {} & \text{ }\!\!|\!\!\text{ } & {} & \text{ }\!\!|\!\!\text{ } & {} \\
\end{matrix}$
Two valencies are involved in forming a double bond.
Similarly, if the carbon consists the triple bond is called the alkyne.in alkyne the $\text{ C-C}$ have triple bonds therefore the general formula is\[\text{ }{{\text{C}}_{\text{n}}}{{\text{H}}_{\text{2n-2}}}\].
$\begin{matrix}
   - & \text{C} & \equiv & \text{C} & - & {} \\
\end{matrix}$
Therefore, the unsaturated hydrocarbons have a lower number of hydrogen than the saturated hydrocarbon (alkane).since the carbon has the tetravalency and the double or triple bond occupies the valency.
Three valencies of carbon are involved in the formation of a triple bond.
Thus, we can say that the unsaturated hydrocarbon contains fewer hydrogen atoms than is needed for carbon to have its usual valency of four

Hence, (B) is the correct option.


Note: saturated hydrocarbon is a hydrocarbon that contains only single bonds between the adjacent carbon atoms. The general formula to exhibit a saturated hydrocarbon is\[\text{ }{{\text{C}}_{\text{n}}}{{\text{H}}_{\text{2n+2}}}\].