Question

Name a metal When calcium metal is added to water the gas evolved does not catch fire but the same gas evolved on adding sodium metal to water catches fire. Why is it so?

Answer 1

In both cases, the gas evolved is H₂. When calcium reacts with water the heat evolved is not sufficient for hydrogen to catch fire. On the other hand, sodium metal reacts with water violently and in this case, a lot of heat is evolved which is sufficient for hydrogen to catch fire.