Question

Why is argon used in lamps?
A. Argon forms molecules when electricity is passed through it.
B. Argon is inert and so does not react with the hot filament.
C. Argon is less dense than air.
D. Argon produces light when it burns.

Answer 1

Hint: Argon is a chemical element with the symbol Ar and atomic number18. It is placed in a group – 18 in the periodic table. Group 18 is known for noble gases or inert gases. Argon is colourless, odourless, non-flammable and non-toxic.

Complete answer:
Argon has several desirable properties like
(a) Argon is a chemically inert gas.
(b) Argon is the cheapest alternative when nitrogen is not sufficiently inert.
(c) Argon has low thermal conductivity.
(d) Argon has electric properties (Ionization and the emission spectrum) desirable for some applications.
As argon is inert it does not react with the hot filament. Argon gas is used in fluorescent and incandescent light bulbs to stop the oxygen in the light bulbs from corroding the hot tungsten filament. The presence of argon in light bulbs prevents the evaporation of the tungsten filament, which results in increased light bulb life. Argon is also used to create an inert atmosphere for growing semiconductor crystals, ore welding and for processes that need protection from other kinds of atmospheric gases.

Thus the correct option is (B).

Note: A 1994 incident in which a man was asphyxiated after entering an argon filled section of oil pipe under construction in Alaska, highlights the dangers of argon tank leakage in confined spaces and emphasizes the need for proper use, storage and handling. Although argon is non-toxic. It is 38 % denser than air and therefore considered a dangerous asphyxiant in a closed area. Argon makes 0.93 % of the earth’s atmosphere, making it the third most abundant gas argon is obtained from the air as a by-product of the production of oxygen and nitrogen.