Question

(a) What will be the action of the following substances on litmus paper?Dry HCl gas, moistened NH3 gas, lemon juice, carbonated soft drink, curd, soap solution.(b) A milkman adds a very small amount of baking soda to fresh milk.(i) Why does he shift the pH of the fresh milk from 6 to slightly alkaline?(ii) Why does this milk take a long time to set as curd?

Answer 1

your question is so long but we prefer only 30 words

Answer 2

Litmus tests

Explanation:

(a) Litmus tests:

1. Dry HCl gas will not change the colour of blue litmus paper.
2. Moistened NH3 gas turns red litmus blue.
3. Lemon juice turns blue litmus red indicating its acidic presence.
4. Carbonated soft drinks turns blue litmus to red.
5. Curd changes blue litmus to red.
6. Soap solution is a base and changes red litmus paper to blue.

(b) When baking soda is added fresh milk, CO2 is forms. So it turns blue litmus to red.

1. As the solution turns slightly alkaline and the pH of the fresh milk will shift from 6.
2. As this milk is slightly more alkaline than other, the acid produced to set into curd will be neutralized by baking soda added by milkman. Hence, this milk takes a longer time to set as curd.