Question

What will happen if a lighted candle is brought near the mouth of a jar containing a) hydrogen gas b) carbon dioxide gas

Answer 1

When a lighted candle is brought near the mouth of the jar containing hydrogen gas, a pop sound is heard and the flame of the candle is extinguished.
And when the lighted candle is brought near the mouth of a jar containing carbon dioxide gas the flame of the candle extinguish without making any sound.
I hope this may help you.

Answer 2

When the lighted candle is brought near the mouth of a jar containing hydrogen gas then the flame of candle is extinguished with a pop sound but                                                    when a lighted candle is brought near the mouth of the jar containing carbon di oxide gas then the flame of candle is extinguish without any sound