Question

A candle brought near the mouth of a jar containing hydrogen gas starts burning but is extinguished when pushed inside the jar.

Answer 1

Hint: Hydrogen gas (${H_2}$) is an odourless, colourless, and tasteless gas. It has many specific properties. Treatment of granulated zinc with dilute hydrochloric acid gives dihydrogen. It can also be prepared by the reaction of Zinc with aqueous NaOH. Dihydrogen is highly stable as it has a high bond enthalpy.

Complete step by step answer:
Dihydrogen is highly combustible. Hydrogen reacts with almost all elements, like oxygen, halogen, nitrogen, and form different compounds.
We know that hydrogen is a combustible gas but does not support combustion.
We know that for a substance to burn, the presence of oxygen is a must. The process is called combustion when any substance burns in the presence of oxygen. It can also be called a scientific name for burning.
Here for a candle to burn, the hot gas reacts with oxygen and we see the flame.
When a candle is brought near the mouth of the jar containing hydrogen, it will react with the oxygen in the air and it will burn.
But if the candle is taken inside the jar containing hydrogen gas, there is no presence of oxygen inside the jar. So there is no oxygen to support combustion. As a result, the candle will not burn.

Note: We also know that during the burning of fuels, it reacts with the oxygen in the air and give products as $C{O_2}$ and ${H_2}O$. Water does not burn even though it contains oxygen and hydrogen. Because the compound formed does not show the properties of hydrogen and oxygen. Thus water is used as a fire extinguisher.