Two statements are given below : Statement I : The melting point of monocarboxylic acid with even number of carbon atoms is higher than that of with odd number of carbon atoms acid immediately below and above it in the series. Statement II : The solubility of monocarboxylic acids in water decreases with increase in molar mass. Choose the most appropriate option :

Both Statement I and Statement II are correct.

Both Statement I and Statement II are incorrect.

Statement I is correct but Statement II is incorrect.

Statement I is incorrect but Statement II is correct.

Aldehydes Ketones and Carboxylic Acids PYQ — JEE Main 2022 · 24 Jun · Shift 1 · Q8 with Solution

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Correct answer: A

Analyze Statement I

Statement I says:

The melting point of monocarboxylic acids with an even number of carbon atoms is higher than that of the odd-carbon acids immediately below and above it in the homologous series.

This is correct.

Reason: In straight-chain monocarboxylic acids, compounds with an even number of carbon atoms pack more efficiently in the crystal lattice than the neighboring odd-carbon members. Better packing leads to stronger intermolecular attractions in the solid state, hence a higher melting point.

This is the well-known odd-even effect in melting points.
Analyze Statement II

Statement II says:

The solubility of monocarboxylic acids in water decreases with increase in molar mass.

This is also correct.

Reason: Lower monocarboxylic acids are quite soluble in water because the $-\mathrm{COOH}$ group can form hydrogen bonds with water. However, as molar mass increases, the hydrocarbon chain becomes longer and more hydrophobic. The nonpolar part starts dominating, so solubility in water decreases.

For example:
- Formic acid and acetic acid are highly soluble in water.
- Higher carboxylic acids become progressively less soluble.
Conclusion
- Statement I: Correct
- Statement II: Correct
Therefore, the correct option is: $\boxed{\text{A}}$
Comparison with stored answer

Stored correct answer: A

My derived answer: A

Hence, my answer agrees with the stored correct answer.

View written solutionFree

Correct answer: A

Analyze Statement I

Statement I says:

The melting point of monocarboxylic acids with an even number of carbon atoms is higher than that of the odd-carbon acids immediately below and above it in the homologous series.

This is correct.

Reason: In straight-chain monocarboxylic acids, compounds with an even number of carbon atoms pack more efficiently in the crystal lattice than the neighboring odd-carbon members. Better packing leads to stronger intermolecular attractions in the solid state, hence a higher melting point.

This is the well-known odd-even effect in melting points.
Analyze Statement II

Statement II says:

The solubility of monocarboxylic acids in water decreases with increase in molar mass.

This is also correct.

Reason: Lower monocarboxylic acids are quite soluble in water because the $-\mathrm{COOH}$ group can form hydrogen bonds with water. However, as molar mass increases, the hydrocarbon chain becomes longer and more hydrophobic. The nonpolar part starts dominating, so solubility in water decreases.

For example:
- Formic acid and acetic acid are highly soluble in water.
- Higher carboxylic acids become progressively less soluble.
Conclusion
- Statement I: Correct
- Statement II: Correct
Therefore, the correct option is: $\boxed{\text{A}}$
Comparison with stored answer

Stored correct answer: A

My derived answer: A

Hence, my answer agrees with the stored correct answer.