When pure water boils vigorously, the bubbles that rise to the surface are composed primarily of
[amp_mcq option1=”air” option2=”hydrogen” option3=”hydrogen and oxygen” option4=”water vapour” correct=”option4″]
This question was previously asked in
UPSC NDA-2 – 2017
Boiling occurs when the vapour pressure of the liquid equals the surrounding atmospheric pressure, and the liquid turns into gas within the bulk of the liquid as well as at the surface. The bubbles formed during boiling are filled with the gaseous form of the liquid, which in this case is water vapour.