Azeotrope Type Based on Intermolecular Forces

❓ Question

Which of the following binary mixtures does not show the behaviour of minimum boiling azeotropes?

$$C_4H_9OH + C_6H_5NH_2$$

$$H_2O + CH_3COCH_3$$

$$CS_2 + CH_3COCH_3$$

$$CH_3OH + CHCl_3$$

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🖼 Question Image

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✍️ Short Explanation

This problem is based on:

👉 Azeotropes
👉 Positive and negative deviation
👉 Intermolecular forces.

Main idea:

$$\boxed{ \text{Minimum boiling azeotrope} \Rightarrow \text{Positive deviation from Raoult’s law} }$$

and

$$\boxed{ \text{Maximum boiling azeotrope} \Rightarrow \text{Negative deviation} }$$

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🔷 Step 1 — Understand Azeotropes 💯

Minimum boiling azeotrope

Occurs when:

$$A-B \text{ interactions are weaker}$$

than:

$$A-A \text{ and } B-B$$

So solution shows:

$$\boxed{ \text{Positive deviation} }$$

Boiling point decreases.

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Maximum boiling azeotrope

Occurs when:

$$A-B \text{ interactions are stronger}$$

So solution shows:

$$\boxed{ \text{Negative deviation} }$$

Boiling point increases.

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🔷 Step 2 — Check Each Option

Option 1

$$C_4H_9OH + C_6H_5NH_2$$

Hydrogen bonding gets disturbed.

Interactions become weaker.

Hence:

$$\boxed{ \text{Positive deviation} }$$

→ Minimum boiling azeotrope possible.

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Option 2

$$H_2O + CH_3COCH_3$$

Acetone weakens water-water H-bonding.

So:

$$\boxed{ \text{Positive deviation} }$$

→ Minimum boiling azeotrope.

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Option 3

$$CS_2 + CH_3COCH_3$$

Weak intermolecular attractions.

Usually shows:

$$\boxed{ \text{Positive deviation} }$$

→ Minimum boiling azeotrope.

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Option 4

$$CH_3OH + CHCl_3$$

Strong hydrogen bonding forms between:

$$O \text{ of methanol}$$

and

$$H \text{ of CHCl}_3$$

So intermolecular attraction becomes stronger.

Hence:

$$\boxed{ \text{Negative deviation} }$$

→ Maximum boiling azeotrope.

Thus it does not show minimum boiling behaviour.

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🔷 Step 3 — Final Identification

Required mixture:

$$\boxed{ CH_3OH + CHCl_3 }$$

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🔷 Step 4 — JEE Trap Alert 🚨

❌ Positive deviation aur negative deviation confuse kar lena

❌ Hydrogen bonding effect ignore kar dena

❌ Minimum boiling ko stronger attraction se relate kar dena

Remember:

$$\boxed{ \text{Stronger attraction} \Rightarrow \text{Higher boiling point} }$$

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✅ Final Answer

$$\boxed{ CH_3OH + CHCl_3 }$$

(Option 4)

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