Two statements are given belwo :
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 :

Options

A. Both Statement I and Statement II are correct.
B. Both Statement I and Statement II are incorrect.
C. Statement I is correct but Statement II is incorrect.
D. Statement I is incorrect but Statement II is correct.

Answer

To solve the question, we need to analyze both statements provided:

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

1. **Understanding Melting Points:**
- Monocarboxylic acids are organic compounds that contain a carboxyl group (-COOH).
- The melting point of these acids can be influenced by their molecular structure, specifically the arrangement of their carbon chains.
- Generally, acids with even-numbered carbon chains can pack more efficiently in a crystal lattice due to their symmetrical structure, leading to stronger intermolecular forces and higher melting points compared to those with odd-numbered carbon chains.

2. **Conclusion for Statement I:**
- This statement is **true** because the even-numbered acids tend to have higher melting points than their odd-numbered counterparts due to better packing in the solid state.

**Statement II:** The solubility of monocarboxylic acids in water decreases with an increase in molar mass.

1. **Understanding Solubility:**
- Solubility in water is influenced by the balance between hydrophilic (water-attracting) and hydrophobic (water-repelling) characteristics of a molecule.
- Monocarboxylic acids have a polar carboxyl group that can form hydrogen bonds with water, making them soluble.
- However, as the carbon chain length increases (higher molar mass), the hydrophobic character of the alkyl chain becomes more dominant, which reduces overall solubility in water.

2. **Conclusion for Statement II:**
- This statement is also **true** because, as the molar mass increases, the solubility of monocarboxylic acids in water tends to decrease due to the increasing hydrophobic nature of the longer carbon chains.

**Final Conclusion:**
Both statements are true.

**Answer: Both Statement I and Statement II are true.**

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