Question

The molecular formula of the organic acid is:
\[
  A.{\text{ }}{C_2}{H_6} \\
  B.{\text{ }}{C_2}{H_5}{O_2} \\
  C.{\text{ }}{C_2}{H_6}{O_2} \\
  D.{\text{ }}{C_2}{H_4}O \\
 \]

Answer 1

Hint: In order to solve the given problem we will first see the basic definition of organic acid along with some examples further on the basis of the options given we will find out the basic types of organic acid that is possible out of the four. Further on the basis of the determined type of organic acid we will see the general formula of carboxylic acid and further we will see that which out of the given options satisfies the general formula of the carboxylic acid and we will select the organic acid out of the four given options.

Complete step by step answer:
Let us first briefly discuss organic acid.
An organic compound with acidic properties is an organic acid. Carboxylic acids, whose acidity is related to their carboxyl group, $ - COOH$ , are the most common organic acids. Relatively stronger acids are sulfonic acids, comprising the group $ - S{O_2}OH$ .
Organic acid is an organic compound which, in the presence of water, is characterised by poor acidic properties and does not dissociate fully.
In general, organic acids are not as strong as inorganic acids. The key distinction between the two is that the product contains sulphur; inorganic acids do not contain carbon.
For a range of uses, organic acids are used, from leather tanning to food additives. Tartaric acid and formic acid include examples of organic acids.
From the given options we can see that in each of the organic compounds there is an absence of sulphur, but there are presence of carbon, oxygen and hydrogen.
The general formula of such organic acid is ${C_n}{H_{2n + 1}}COOH$ .
This general formula of these types of organic acid can also be written as:
$
   \Rightarrow {C_n}{H_{2n + 1}}COOH \\
   \Rightarrow {C_n}{H_{2n + 2}}{O_2} \\
   \Rightarrow {C_n}{H_{2n + 2}}{O_2} \\
 $
So, if the value of n=1 the organic acid must have 2 carbon atoms, 6 hydrogen and 2 oxygen atoms.
This is fulfilled by the compound \[{C_2}{H_6}{O_2}\] .
Hence, the molecular formula of the organic acid is \[{C_2}{H_6}{O_2}\] .
So, the correct answer is “Option C”.

Note: This problem can also be solved by the method of stoichiometry by finding the weights of different atoms on the basis of the reaction when carbon dioxide gas is absorbed by the potassium hydroxide solution in the presence of organic acid. Then the ratio of weight of carbon and hydrogen is found out to be three times and further on the basis of this ratio the correct option is selected. But here we have used a simpler method to find out the ratio.