Question

What happens when calcium is treated with water? (i) it does not react with water (ii) it reacts violently with water (iii) it reacts less violently with water (iv) bubbles of hydrogen gas formed stick to the surface of calcium?

Answer 1

Answer:

(iii) and (iv)

Explanation:

Ca(OH)2 is formed along with H2 gas which sticks to the surface

Answer 2

As per given condition, Calcium reacts with water.

When Calcium reacts with waters following reaction takes place.

$\sf{Ca(s)+H_2O(l) \rightarrow Ca (OH)_2(aq)+H_2(g)\:(heat)}$

Balanced equation:

$\sf{Ca(s)+2H_2O(l) \rightarrow Ca (OH)_2(aq)+H_2(g)\:(heat)}$

When Calcium reacts with water formation of Calium Hydroxide i.e. Slaked lime takes place. Also, formation of Hydrogen gas takes place.

The above reaction is Exothermic Reaction because it release energy in the form of heat.

i) It does not react with water: The given option is wrong. Because Calcium reacts with water and formation of Calcium Hydroxide and Hydrogen gas takes place.

ii) It reacts violently with water: The given process is slow. So, it can't react quickly with water. So, option is wrong.

From above we can say that option iii) and iv) are correct: As it takes time and formation of hydrogen gas takes place. The released Hydrogen gas stick to the surface of Calium.

To check the presence of Hydrogen gas. Bring a burning matchstick near the mouth of test tube. If it burns with a 'pop' sound then Hydrogen gas is present.