pH in Digestive System
Our stomach has an acidic medium due to the secretion of HCl that helps digest our food. At times when we suffer from indigestion which also leads to excess acid formation in the stomach, we feel uncomfortable. To neutralise the effect of the excess acid , we use antacids which are basic in nature.
The antacid neutralises the excess acid and thus gives relief to the person. The most commonly used antacid is Magnesium Hydroxide (Mg(OH) 2 ) also commonly known as Milk of Magnesia.
Tooth Decay :
Tooth Decay starts when the pH of our mouth falls below 5.5.
This happens due to acids released by bacteria while breaking down sugar in our mouth.
Toothpastes usually contain a mild base to neutralise such acids in your mouth to prevent the enamel from getting corroded due to the acids.
Plants and Animals are pH sensitive :
Our body works between a pH of 7-7.8. All living beings are extremely sensitive to pH change and extreme change can make it difficult for the existence of life.
Acid rain, which is rain water mixed with acids and thus having a pH of less than 5.5 , when falls into rivers , changes the pH levels of the river water and thus kills aquatic life. Similarly acid rain on plants also kills them as they require a certain pH of soil to thrive.
Self Defence in Animals and Plants :
When ants sting a person , they inject methanoic acid into the skin which causes extreme burning and irritation. When a wasp stings a person , they inject a basic liquid onto the skin which again causes immense discomfort.
In such cases corresponding acids or bases are used to neutralise the effect of stings from insects. For an ant bite , often a mild base like baking soda can be rubbed onto the sting to neutralise the effect of acid. And for the wasp sting , a mild acid like vinegar is rubbed to neutralise the effect of the base. Many other animals as well as plants such as the nettle plant use this mechanism as a defense in the wild.