Question

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

Answer 1

Because there is no carbon dioxide.

Answer 2

$\huge\star\underbrace{\mathtt\red{✺A} \mathtt\green{N}\mathtt\blue{S} \mathtt\purple{W}\mathtt\orange{E} \mathtt\pink{R✺}}\star⋆$

because it runs out of Oxygen