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

• A. (i) and (iv)
• B. (ii) and (iii)
• C. (i) and (ii)
• D. (iii) and (iv)

Answer 1

The correct option is D

(iii) and (iv)

The explanation for correct option:

D. (iii) and (iv)

The reaction of Calcium with water:

• When calcium $\left(\mathrm{Ca}\right)$ reacts with water $\left({\mathrm{H}}_2\mathrm{O}\right)$, calcium hydroxide $\left(\mathrm{Ca}{\left(\mathrm{OH}\right)}_2\right)$ is formed along with the liberation of hydrogen gas $\left({\mathrm{H}}_2\right)$. The bubbles of hydrogen gas get stick to the surface of calcium.
• The reaction is less violent in nature.
• The chemical equation can be depicted as:

$\mathrm{Ca}\left(\mathrm{s}\right)+2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)\to \mathrm{Ca}{\left(\mathrm{OH}\right)}_2\left(\mathrm{aq}\right)+{\mathrm{H}}_2\uparrow$

Explanation for incorrect options

Option A: (i) is incorrect as calcium reacts with water while (iv) is correct that bubbles of hydrogen gas formed stick to the surface of calcium. Therefore, this option stands incorrect.

Option B: (ii) is incorrect, as calcium reacts less violently with water while (iii) is correct. Thus, this option stands incorrect.

Option C: Calcium reacts less violently with water.

Hence, option D i.e. (iii) and (iv) is correct.