The correct option is (a).
Explanation
Hydrogen ($H_2$) is a diatomic gas known for its specific chemical properties, particularly its high combustibility and reaction with oxygen. Identifying these properties is essential for distinguishing hydrogen from other gases in a laboratory setting.
Statement-wise Analysis
- Statement 1 is Correct: Hydrogen is a highly combustible gas. It reacts rapidly with oxygen (combustion) to form water ($H_2O$) and releases a significant amount of energy.
- Statement 2 is Incorrect: While a continuous jet of pure hydrogen may burn quietly, the characteristic test for hydrogen gas involves bringing a burning candle or splint near the gas. In this scenario, it burns with a distinctive "pop" sound (a small explosion) due to the rapid reaction with oxygen in the air. It is not described as burning silently in the context of identification.
- Statement 3 is Incorrect: Pure hydrogen gas is colourless, odourless, and tasteless. It does not possess a pungent odour. Gases with pungent odours include ammonia ($NH_3$) or sulphur dioxide ($SO_2$).
Key Takeaway
Hydrogen is a combustible, odourless gas that is identified by the "pop" sound produced when it burns in the presence of air.