The acid produced naturally in our stomach is:

50 It has been found that rubbing vinegar on the stung area of the skin of a person gives him relief. The person has been stung by: 51 Fresh milk has a pH of 6. When milk changes into curd, the pH value will: 53 The daffodil plants grow best in a soil having a pH range of 6.0 to 6.5. If the soil in a garden has a pH of 4.5, which substance needs to be added to the soil in order to grow daffodils? 54 A milkman adds a very small amount of baking soda to fresh milk.

(a) Why does he shift the pH of the fresh milk from 6 to slightly alkaline?

(b) Why does this milk take a long time to set as curd?