Question

How many isomers have the formula ${C_3}{H_8}$?

Answer 1

As we know that the isomer is basically defined as the compounds possessing the same molecular formula but arrangement of atoms is different in the molecule possessing different chemical and physical properties.

Complete step-by-step answer:
As we know that the hydrocarbons are named according to the number of carbon atoms present in the organic molecule and they start with the naming of the compound as methane, ethane, propane and so on which possess $1,2,3..$ and so on carbon atoms.

The arrangement of these carbon and hydrogen atoms is different in each compound but these compounds possess similar chemical formulas and thus their chemical and physical properties are different. For instance: Methane possessing one carbon can only be written as $C{H_4}$ and ethane with two carbon atoms can only be written as $C{H_3} - C{H_3}$ and therefore, both of them can form one isomer only.

Thus, we can say that ${C_3}{H_8}$ which is propane and is made up of three carbon atoms and eight hydrogen atoms which can be arranged in a straight chain of alkane only and thus only one isomer is possible for propane and is given as shown below:
${H_3}C - C{H_2} - C{H_3}$

We cannot arrange these three carbons in any other manner and that is why this is the only possible isomer and therefore, the correct answer is one.

Note: Always remember that an isomer can be defined as the different arrangement of carbon and hydrogen atoms but the number remains the same like a butane can have two isomers one is $n - butane$ and other is isobutene. Similarly, pentane can have three isomers and so on.