Answer :
The required "option b) is not true about a hydrate".
Explanation:
- The Residue of hydrate is insoluble so as to filter it out.
- The Presence of hydrated water may evaporate during heating of the residue.
- During dehydration, there is a color change that is when water is given off.
- Therefore, the hydrate will not revert to its original color on the addition of water.
Thus, the required "option b) is not true about a hydrate".