Three hydrocarbons P, Q and R are shown below:
`P : CH_(3)CH_(2)CH_(2)CH_(3),Q : CH_(3) - C-= C - CH_(2)CH_(3)`
`R: CH_(3)CH_(2) -CH = CH - CH_(3)`
Identify the correct statement(s) about these three hydrocarbons.
I. P and both differ by a `-CH_(2)` unit.
II. Q and R are saturated hydrocarbons.
III. P, Q and R, all have different general formulae.
IV. Q and R are isomers.

Options

A. I and II only
B. II and III only
C. I and IV only
D. III only

Answer

To solve the problem, we need to analyze the three hydrocarbons P, Q, and R, and evaluate the given statements one by one.

### Step 1: Identify the hydrocarbons and their formulas
1. **Hydrocarbon P**: CH₃CH₂CH₂CH₃
- This is butane (C₄H₁₀).
- Number of Carbon (C) = 4
- Number of Hydrogen (H) = 10
- General formula: CₙH₂ₙ₊₂ (for n=4, C₄H₁₀)

2. **Hydrocarbon Q**: CH₃ - C≡C - CH₂CH₃
- This is 1-pentyne (C₅H₈).
- Number of Carbon (C) = 5
- Number of Hydrogen (H) = 8
- General formula: CₙH₂ₙ₋₂ (for n=5, C₅H₈)

3. **Hydrocarbon R**: CH₃CH₂ - CH = CH - CH₃
- This is 2-pentene (C₅H₁₀).
- Number of Carbon (C) = 5
- Number of Hydrogen (H) = 10
- General formula: CₙH₂ₙ (for n=5, C₅H₁₀)

### Step 2: Evaluate the statements
1. **Statement I**: P and R differ by a -CH₂ unit.
- P (C₄H₁₀) and R (C₅H₁₀) differ by a -CH₂ unit.
- **This statement is correct.**

2. **Statement II**: Q and R are saturated hydrocarbons.
- Saturated hydrocarbons contain only single bonds.
- Q has a triple bond and R has a double bond.
- **This statement is incorrect.**

3. **Statement III**: P, Q, and R all have different general formulae.
- P: C₄H₁₀, Q: C₅H₈, R: C₅H₁₀.
- They have different general formulas.
- **This statement is correct.**

4. **Statement IV**: Q and R are isomers.
- Isomers have the same molecular formula but different structures.
- Q (C₅H₈) and R (C₅H₁₀) have different molecular formulas.
- **This statement is incorrect.**

### Conclusion
The correct statements are:
- I: P and R differ by a -CH₂ unit (Correct)
- III: P, Q, and R all have different general formulae (Correct)

### Final Answer
The correct statements are I and III.

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