When a molten ionic hydride is electrolysed:

The products formed when heavy water is reacted with magnesium nitride are:

Which of the following can be added to remove the permanent hardness of water?

Which of the following ions are responsible for the hardness of water?

Assertion $(A)$ : $NaCl$ is less soluble in heavy water than in ordinary water.
Reason $(R)$ : Dielectric constant of ordinary water is more than that of heavy water.
The correct answer is

What is meant by 'demineralised' water and how can it be obtained?