Question

Assertion: Chemical formula of n-propane and isopropane is the same.
Reason: n-propane doesn’t exhibit chain isomerism
A.Both Assertion and Reason are correct and Reason is correct explanation for Assertion
B.Both Assertion and Reason are correct But the Reason is not the correct explanation for Assertion
C.Assertion is incorrect but Reason is correct
D.Both Assertion and Reason are correct

Answer 1

In this question, we are discussing the existence of chain isomerism in different compounds like n-propane and isopropane with their different structures or not. So, accordingly choose one option that will be suited to the above condition.

Complete step by step answer:
Let us first understand what is isomerism
When two or more compounds have the same molecular formula but different chemical and physical properties , they are called isomers and the phenomenon is known as isomerism .
It is of various types , In this question we need to learn about chain isomerism only , so
Compounds having the same molecular formula but different arrangement of carbon chains within the molecule are called chain isomers and the phenomenon is known as chain isomerism .
Now let us take the case of n-propane and isopropane
The prefix n is used in front of those compounds which do not have any branches , that is they are linear chain compounds .
So n-propane is $C{H_3} - C{H_2} - C{H_3}$
Also the prefix iso is used when in a hydrocarbon chain one alkyl group is present on the second last carbon atom.
So isopropane is $C{H_3} - C{H_2} - C{H_3}$
As you can see from the above two structures that both the structures are the same , this is because for a compound to show isomerism it should have a minimum of four carbon atoms and in case of propane we have only three.
So , no matter how we arrange the carbon atoms we will get the same structure every time .
Hence we find out that the chemical formula of n-propane and isopropane is the same and n-propane does not show isomerism .
So , option A is correct .

Note: For chain isomerism ,be careful not to draw "false" isomers which are just twisted versions of the original molecule. For example, this structure is just the straight chain version of butane rotated about the central carbon-carbon bond. ( this does not count for a different isomer )