Question

7. When calcium metal is added to water, the gas evolved does not catch fire; instead calcium
float on water. But on adding potassium metal to water, the same gas evolved catches. Fire
Explain why? Give equation of reaction.​

Answer 1

In both cases, the gas evolved is

H2

. When calcium reacts with water the heat evolved is not suffcient for hydrogen to catch fire. On the other hand, pottasium metal reacts with water violently and in this case a lot of heat is evolved which is sufficient for hydrogen to catch fire.