Question

<!--td {border: 1px solid #ccc;}br {mso-data-placement:same-cell;}--> How do you confirm the presence of hydrogen gas?

Answer 1

<!--td {border: 1px solid #ccc;}br {mso-data-placement:same-cell;}--> When a burning matchstick or candle is brought near the hydrogen gas, the burning matchstick goes off with a pop sound.
The reaction of a metal with acid results in the formation of hydrogen gas, which is further confirmed by the above test.