Question

The empirical formula of an acid is ${C_2}{H_4}O$, the probable molecular formula of acid may be:

{A:{\text{ }}{C_4}{H_9}COOH} \\\ {B:{\text{ }}{C_3}{H_7}COOH} \\\ {C:{\text{ }}{C_2}{H_5}COOH} \\\ {D:{\text{ }}C{H_3}COOH} \end{array}$$

Answer 1

Hint : Empirical formula of a compound depicts the simplest whole number ratio of the atoms present in a compound while molecular formula depicts the number of every atom present in a molecule. On the other hand, the structural formula depicts how atoms present in a molecule are being bonded to one another.

Complete Step By Step Answer:
Molecular formula represents the exact number of all of the atoms present in a molecule or compound. But, empirical formula represents the ratio of those atoms in a molecule or compound. Thus we can say that the relationship that exists between the molecular formula and the empirical formula can be represented as follows:
$Molecular{\text{ }}formula = {(Empirical{\text{ }}formula)_n}$
Where n refers to an integer
In the given question, we are provided with the empirical formula of an acid as ${C_2}{H_4}O$, and we have to find out the probable molecular formula of this acid.
Using the aforementioned relation between empirical and molecular formula, the molecular formula of the desired acid should be $({C_2}{H_4}O)n$, where n refers to an integer.
Now, let us suppose that value of n is 2, then the molecular formula of the acid becomes $({C_2}{H_4}O)2 = {C_4}{H_8}{O_2}$which is Ethyl acetate and can be written as $C{H_3}COOH$.
Now, if we look at the options, the correct answer is Option B.
In the question the ratio of carbon, hydrogen and oxygen is 2:4:1 and in Option A, C and D it is 5:10:2, 3:6:2 and 2:4:2. Thus, these options can’t be correct.

Note :
If we know the molar mass of any unknown compound, we can find the molecular formula of that compound from its empirical formula by comparing the empirical formula mass with the molar mass of the compound.