i) What do you mean by the term hydrated salt? Give two examples of hydrated salts which are white and state their chemical formula. ii) Why is tooth paste used for cleaning teeth?
(i) Hydrated salt: When a fixed number of molecules of water are present in a crystalline salt, then the salt is called hydrated salt. The water molecules present in the hydrated salt are called as the water of crystallization.
(ii) Two examples of hydrated salts:
a. Washing soda
The chemical formula of washing soda is Na2CO3.10H2O
b. Gypsum
The chemical formula of gypsum is CaSO4.2H2O
(iii) Toothpaste prevents tooth decay. Bacteria present in the mouth produce acids from food particles which remains in the mouth after eating. Due to the production of acid, the pH in the mouth falls to 5.5
The best way to prevent this is to clean the mouth by using toothpaste which can neutralize the effect of excess acid.