CBSE Class 10 Science Carbon And Its Compounds Worksheet Set A - Free Printable

You're absolutely correct — the image you uploaded contains Question 6, which asks to draw the structures for four compounds and also explores structural isomerism in bromopentane.

Let’s go through each part step-by-step with explanations, even though you’ve already provided the answer. This will help reinforce understanding.

---

## ✔ (i) Ethanoic Acid – CH₃COOH

Explanation:
- “Ethanoic acid” is the IUPAC name for acetic acid.
- The root “eth-” means 2 carbon atoms.
- “-oic acid” indicates a carboxylic acid functional group (–COOH).
- So, structure: CH₃–COOH

Structural Diagram (as shown):
```
H O
| ||
H - C - C - OH
|
H
```

This is a carboxylic acid with a methyl group (CH₃–) attached to the carbonyl carbon.

---

## ✔ (ii) Bromopentane – C₅H₁₁Br

Explanation:
- “Pentane” = 5 carbon chain (alkane).
- “Bromo-” = bromine atom substituent.
- Formula: C₅H₁₁Br — this confirms it’s a monosubstituted pentane (one H replaced by Br).

Important Note:
✔ *Are structural isomers possible for bromopentane?* → YES!

Because the bromine can attach to different carbon atoms in the pentane chain, we get positional isomers.

Structural Isomers of Bromopentane:

1. 1-Bromopentane: Br on terminal (C1)
```
Br-CH₂-CH₂-CH₂-CH₂-CH₃
```

2. 2-Bromopentane: Br on C2
```
CH₃-CH(Br)-CH₂-CH₂-CH₃
```

3. 3-Bromopentane: Br on C3
```
CH₃-CH₂-CH(Br)-CH₂-CH₃
```

> ⚠️ Note: 2-Bromopentane and 3-Bromopentane are not identical because the carbon chain is asymmetric — they are distinct positional isomers. Also, 2-bromopentane has a chiral center, so it has stereoisomers too — but the question only asks for *structural* isomers (constitutional isomers), so 3 isomers total.

✔ So yes — bromopentane has 3 structural isomers.

---

## ✔ (iii) Butanone – C₂H₅COCH₃

Explanation:
- “Butanone” = ketone with 4 carbon atoms.
- “-one” = ketone functional group (>C=O) in the middle of the chain.
- Structure: CH₃–CO–CH₂–CH₃ or written as C₂H₅–CO–CH₃ (ethyl methyl ketone)

Structural Diagram (as shown):
```
H O H H
| || | |
H - C - C - C - C - H
| | |
H H H
```

Actually, better drawn as:
```
O
||
CH₃-C-CH₂-CH₃
```

This is methyl ethyl ketone, a common solvent.

---

## ✔ (iv) Hexanal – C₅H₁₁CHO

Explanation:
- “Hexanal” = aldehyde with 6 carbon atoms.
- “-al” = aldehyde group (–CHO) at end of chain.
- So, 5 carbons in chain + CHO = 6 total carbons.
- Formula: C₆H₁₂O (since CHO contributes one carbon and the H in CHO is included; C₅H₁₁CHO = C₆H₁₂O)

Structure:
```
O
||
CH₃-CH₂-CH₂-CH₂-CH₂-CHO
```

Or expanded as shown in your image:
```
H H H H H O
| | | | | ||
C - C - C - C - C - C - H
| | | | | |
H H H H H H
```

Wait — actually, the last carbon should be the aldehyde carbon, so it should have double bond to O and single bond to H, not two H’s. The diagram in your image correctly shows:

```
O
||
... - C - H
```

So it’s correct — hexanal is a straight-chain aldehyde with 6 carbons.

---

## 🧠 Summary:

| Compound | Molecular Formula | Functional Group | Notes |
|------------------|-------------------|----------------------|----------------------------------------|
| Ethanoic acid | CH₃COOH | Carboxylic acid | Simplest carboxylic acid |
| Bromopentane | C₅H₁₁Br | Alkyl halide | 3 structural isomers possible |
| Butanone | CH₃COCH₂CH₃ | Ketone | Methyl ethyl ketone |
| Hexanal | C₅H₁₁CHO (C₆H₁₂O) | Aldehyde | 6-carbon straight-chain aldehyde |

---

## ✔ Final Answer Recap (as per your image):

✔️ (i) Ethanoic acid – CH₃COOH
✔️ (ii) Bromopentane – C₅H₁₁Br → 3 structural isomers (1-, 2-, and 3-bromopentane)
✔️ (iii) Butanone – C₂H₅COCH₃
✔️ (iv) Hexanal – C₅H₁₁CHO

All structures and explanations are correct as shown!

Let me know if you’d like to explore *stereoisomers* of 2-bromopentane or naming rules further!