Account for the following :
(a) Antacid tablets are used by a person suffereng from stomach pain.
(b) While diluting an acid, why is it recommended that the acid should be added to water and not water to the acid ?

Explanation

(a) The stomach ache or pain is generally due to the release of excess of acid like HCl. The antacid tablets contain either sodium hydrogen carbonate or magnesium hydroxide. Both enutralise the effect of acid by reacting with it and give relief from the pain.
(b) The process of dilution of acid in water is exothermic in nature. In order to control the heat, it is always better to add acid slowly or dropwise to water taken in a container and not water to acid.