JEE Chemistry 2026 Question with Solution

Given: Compound $x$ has percentage composition $76.6\%\ C$, $6.38\%\ H$ and vapour density $47$. Compound $y$ gives a characteristic colour with neutral $\mathrm{FeCl_3}$ solution.

Find: The incorrect statement.

From vapour density,

$$\text{Molecular mass} = 2 \times 47 = 94$$

Let the molecular formula be $\mathrm{C_xH_yO_z}$.

From percentage composition,

$$\frac{12x}{94} \times 100 = 76.6 \Rightarrow x \approx 6$$ $$\frac{y}{94} \times 100 = 6.38 \Rightarrow y \approx 6$$

Thus, compound $x$ is $\mathrm{C_6H_6O}$, which is phenol.

The reaction with $\mathrm{CO_2 + NaOH}$ under high pressure and temperature followed by acidification is the Kolbe–Schmitt reaction. Therefore, compound $y$ is salicylic acid.

Salicylic acid gives a characteristic colour with neutral $\mathrm{FeCl_3}$, which supports this identification.

Now evaluate the statements:

(A) Salicylic acid contains a $-\mathrm{COOH}$ group and reacts with $\mathrm{NaHCO_3}$ to release $\mathrm{CO_2}$ gas. Hence this statement is correct.

(B) Both phenol and salicylic acid are aromatic compounds, so they burn with a sooty flame. Hence this statement is correct.

(C) Phenol is less acidic than salicylic acid. Salicylic acid is significantly more acidic because of the carboxylic acid group. Therefore this statement is incorrect.

(D) Both phenol and salicylic acid dissolve in $\mathrm{NaOH}$ due to salt formation. Hence this statement is correct.

Therefore, the incorrect statement is C.

Given: The empirical information for compound $x$ and the reaction conditions.

Find: The identities of $x$ and $y$ before checking the statements.

First identify $x$ using molecular mass and composition.

$$\text{Molecular mass of } x = 2 \times 47 = 94$$

For carbon,

$$\frac{12x}{94} \times 100 = 76.6$$

which gives $x \approx 6$.

For hydrogen,

$$\frac{y}{94} \times 100 = 6.38$$

which gives $y \approx 6$.

So the formula is $\mathrm{C_6H_6O}$. The common aromatic compound with this formula is phenol.

Next identify $y$. Phenol on treatment with $\mathrm{CO_2/NaOH}$ under pressure and temperature followed by acidification gives salicylic acid by the Kolbe–Schmitt reaction.

Also, neutral $\mathrm{FeCl_3}$ gives a characteristic colour with phenolic compounds such as salicylic acid. Hence $y$ is salicylic acid.

Since phenol is less acidic than salicylic acid, option C is the incorrect statement.