Question

How many Structure isomers, can you draw for pentane?
A. 2
B. 3
C. 4
D. 5

Answer 1

Hint: Pentane means alkane with 5 carbon atoms. Isomers are compounds with the same formula but different arrangement of atoms and give rise to different properties.

Complete step by step answer:
The chemical formula of pentane is $C_5{H}_{12}$
This hydrocarbon belongs to the Alkane family.
Arrange all 5 Carbon atoms in a straight chain initially.
Then make a chain of 4 carbon atoms, and place another carbon at 2nd position carbon.
Then make a chain of 3 carbon atoms and place 2 carbon atoms, on a middle carbon atom.
This gives rise to a total of 3 structures.

Other than these 3 structures, all are redundant, meaning repeating structure.
In order to know whether a structure is repeating or not, we use IUPAC nomenclature.
Those with the same name are the same structures, even though they may apparently appear to be different.

The correct option is B i.e. smell.

Additional information: The compounds which have only Hydrogen and carbon are called hydrocarbons. There are 3 broad categories of straight chain hydrocarbon- Alkane, alkene and alkyne. The general formula are $$C_n{H}_{2n+2},C_n{H}_{2n},C_n{H}_{2n-2}$$ respectively.

Note:
Take care of repeating structures. Repeating structures can be known by writing IUPAC names of drawn structures.