(a) Why does calcium start floating when added to water?
(b) Most of the metals do not give hydrogen while reacting with nitric acid. Why?
(c ) Write equation for the reaction of iron with steam. Name the compound of iron obtained.

Explanation

(a) The reaction of calcium with water is less violent. The heat evolved is not sufficient for hydrogen to catch fire.
`Ca(s)+2H_(2)O(l) to Ca(OH)_(2)(aq) +H_(2)(g)`
Calcium starts floating because the bubbles of hydrogen gas formed stick to the surface of the metal.
(b) Most of the metals do not give hydrogen while reacting with nitric acid because `HNO_(3) ` is a strong oxidising agent. It oxidises the `H_(2)` produced to water `(H_(2)O)` adn itself gets reduced to any of the nitrogen oxides `(N_(2)O,NO,NO_(2)).`
(c ) Iron reacts with steam to form iron oxide and hydrogen
`3Fe (s)+4H_(2)O(g) to Fe_(3)O_(4)(s)+4H_(2)(g)`