Question

Hydrogen burns in the air with

• A. Light bluish flame
• B. Green flame
• C. Yellow flame
• D. None of these

Answer 1

The correct option is A

Light bluish flame

Explanation:

Combustion is a chemical process in which a substance reacts rapidly with oxygen and gives off heat.

Explanation for Correct answer

• Hydrogen burns with a light blue flame that is nearly invisible in daylight.
• The flame may appear yellow if there are impurities in the air like dust or sodium.
• When hydrogen is “burning”, it undergoes a chemical reaction where it combines with oxygen to form water releasing a lot of energy as:
  $2{\mathrm{H}}_{2\left(\mathrm{g}\right)}+{\mathrm{O}}_{2\left(\mathrm{g}\right)}\to 2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{aqu}\right)+\mathrm{Energy}$
  a lot of energy is released by hydrogen when it combusts, and most of this energy is released in the form of heat.
• Heat causes gases to expand, and since a lot of heat is released the gaseous mixture (hydrogen, oxygen remaining and water vapour liberated from the reaction) and the air adjacent to it expands very quickly, such that the gas molecules break the sound barrier.

Therefore the correct option is (B) i.e light Bluish flame