Q61 of 270 Page 82

Explain why the pH in a person's mouth becomes lower after each meal.

Bacteria present in the mouth produce acids by degradation of sugar and food particles remaining in the mouth after eating. This lowers the pH of the mouth of the person.

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59 Solution A turns universal indicator blue to purple whereas solution B turns universal indicator orange to red.

(a) What will be the action of solution A on litmus?


(b) What will be action of solution B on litmus?


(c) Name any two substances which can give solutions like A.


(d) Name any two substances which can give solutions like B.


(e) What sort of reaction takes place when solution A reacts with solution B?

 60 A first-aid manual suggests that vinegar should be used to treat wasp stings and baking soda for bee stings.

What does this information tell you about the chemical nature of:


(a) wasp stings?


(b) bee stings?

 61 What damage could be caused while the pH is low? 61 How could the person change his eating habits to lessen chances of suffering from tooth decay?