Question

Which of the following is a gas at 300K?

• A. Chloroethane
• B. Bromoethane
• C. Iodoethane
• D. 1-Chloropropane
• E. 1-Bromopropane

Hint:

Remember that only the first few members (C1 and C2 chlorides/bromides) are gases. Everything else, including almost all alkyl iodides, starts as liquids at room temperature.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
The physical state of haloalkanes depends on their boiling points, which are determined by molecular mass and van der Waals forces.
Room temperature (standard) is usually taken as \(298\text{ K} - 300\text{ K}\) (\(\approx 25^\circ\text{C} - 27^\circ\text{C}\)).

Step 3: Detailed Explanation:
Lower members of the alkyl halide series like methyl chloride (\(CH_3Cl\)), methyl bromide (\(CH_3Br\)), and ethyl chloride (\(CH_3CH_2Cl\), also known as chloroethane) are gases at room temperature.
As the number of carbon atoms or the size of the halogen increases, the boiling point rises.
- Chloroethane has a boiling point of approx \(12.3^\circ\text{C}\) (which is \(< 300\text{ K}\)), so it exists as a gas.
- Bromoethane (\(38^\circ\text{C}\)) and higher members are liquids at \(300\text{ K}\).

Step 4: Final Answer:
Chloroethane is a gas at 300K.