Give reason-
a. Fresh milk has a pH of 6. When it changes into curd, its pH value will increase or decrease.
b. pH change in the lake water can endanger the lives of aquatic animals.
c. It is wrong to treat a bee sting with vinegar.
d. Plaster Of Paris should be stored away from moisture.
e. It is recommended that the acid should be added in water and not water in acid.
Answers
Answer:
a. Fresh milk has a pH of 6. When it changes into curd, its pH value will decrease.
Explanation: The pH of milk is 6 while that of curd is of the range 4.5-5.5. The pH decreases as milk changes into curd. This is because of the formation of lactic acid which is acidic in nature.
b. pH change in the lake water can endanger the lives of aquatic animals.
Explanation: When the pH of rain water is nearly 5.6, it is known acid rain. ... This high acidity of water can endanger the live of aquatic animals. To prevent the fish from being killed calcium carbonate is often added to water which neutralizes the acid that came from acid rain.
c. It is wrong to treat a bee sting with vinegar.
Explanation: Since vinegar is acetic acid so it can’t be used to treat bee sting because bee injects acid into the skin.
d. Plaster Of Paris should be stored away from moisture.
Explanation: Plaster of Paris, quick-setting gypsum plaster consisting of a fine white powder (calcium sulphate hemihydrate), which hardens when moistened and allowed to dry because plaster of Paris turns into Gypsum after reacting with moisture present in air. That’s why plaster of Paris should be stored in a moisture-proof container.
e. It is recommended that the acid should be added in water and not water in acid.
Explanation: If you add water to acid it forms an extremely concentrated solution of acid initially. So much heat is released that the solution may boil very violently, splashing concentrated acid out of the container and all this because the reaction is exothermic. ... So it is always safer to add acid to water, and not water to acid.