Question

10. (a) How is pH scale related to hydronium ion concentration?
(b) Explain any two roles played by pH levels of various chemicals on living organisms.
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Answer 1

pH = -log [H+]

pH of blood = 7.2

pH of stomach fluid < 3. Because food digestion takes place only at this level.

Answer 2

a) If hydronium ion concentration increases, then pH value decreases and become acidic in nature.

b) 1)  pH in stomach -

We know that our stomach produces hydrochloric acid, which helps in the digestion of food without harming the stomach. During indigestion, the stomach produces too much acid and this causes pain and irritation. To get rid of this pain, people use bases called antacids. These antacids neutralize the excess acid.

Ex - Magnesium hydroxide ( milk of magnesia )

2) pH in self defence by animals -

Let us take an example of bee stung.

Bee sting leaves methanoic acid which causes pain and irritation. By using a mildbase like baking soda on the stung area gives relief.

Hope it helps you !