Which of the following is used as fuel in miners' lamp?

Analysis

The question asks for the specific hydrocarbon used as a fuel in a miner's lamp. This is a classic application of the properties of alkynes in industrial and practical settings.

Concept Explanation

• Ethyne ($C_2H_2$): Also known as acetylene, this is an alkyne. When ethyne burns in oxygen, it produces an exceptionally hot, bright, and luminous flame. Because of this high luminosity and heat, it was historically used in "carbide lamps" (or acetylene lamps) by miners to provide light in underground tunnels.
• Ethanal ($CH_3CHO$): This is an aldehyde, not a fuel used for lighting.
• Ethene ($C_2H_4$): This is an alkene used primarily in the production of plastics (like polythene) and for fruit ripening.
• Ethane ($C_2H_6$): This is an alkane used mainly as a fuel for heating or as a feedstock in the petrochemical industry, but it does not produce the intense, bright light required for a miner's lamp.

Step-by-Step Solution

1. Identify the requirement: A miner's lamp requires a fuel that produces a bright, steady, and luminous flame to ensure visibility in dark, underground environments.
2. Evaluate the options: • Ethyne ($C_2H_2$) undergoes combustion: $2C_2H_2 + 5O_2 \rightarrow 4CO_2 + 2H_2O + \text{Heat/Light}$. • The reaction releases a significant amount of energy and produces a very bright white light, which is ideal for illumination.
3. Conclusion: Among the given options, Ethyne is the only one with the chemical properties suitable for use in a miner's lamp.

Exam Tip

Whenever you see questions about Ethyne (Acetylene), remember two key uses:

1. Oxy-acetylene welding: Used for cutting and welding metals due to its high flame temperature.
2. Miner's lamp: Used for its high luminosity (brightness).