(a) Mention the pH range within which our body works. Explain how antacids
give relief from acidity. Write the name of one such antacid.
(b) Fresh milk has a pH of 6. How does the pH will change as it turns to curd? Explain your answer.
(c) A milkman adds a very small amount of baking soda to fresh milk. Why does this milk take a longer time to set as curd?
(d) Mention the nature of toothpastes. How do they prevent tooth decay?
Answers
(a)
The pH range required by our blood is from 7.0 to 7.8
Acidity occurs when excess of HCl is released in our stomach. The antacids are basically bases which neutralises the acids to form salt and water. Example-Mg(OH)2
(b)
The pH of the milk becomes lower on its conversion.It is so because curd is made up of lactic acid. On undergoing conversion the milk now turns from a neutral solution to an acidic one which results in decreasing of pH as acids have lower pH
(c)
As baking soda is a base, on it being added to milk it increases the pH of the milk and doesn’t so easily provide the favourable conditions for fermentation.
(d)
Toothpastes are basic in nature . For the decaying of tooth a pH of 5.0 to 5.8 is required. The toothpaste being a base reacts with the acids present in the mouth to ensure the pH of the mouth doesn’t get lower and thus prevents tooth decay.