Chapter 5


Acids, bases and salts

1. Write the difference between acids and bases. 

Answer:  The difference between acid and base is that acid is bitter but base tastes bitter and tastes like soap and water to the hair. Acids turn blue litmus red but bases turn red litmus blue. Acids contain hydrogen but bases contain hyhydroxyls.

2.  Many household products, such as window cleaners, contain ammonia. It turns red litmus blue. What is the nature of it?

Answer:   It is alkaline in nature.

3. Name the source of the litmus solution. What is the use of this solution? 

Answer:  The source of litmus solution is called umbrella algae. This solution can be used to test whether a solution is acid, base or salt.

4. Is the water in the pot acidic, alkaline or neutral? How would you prove this?

Answer:  If a piece of red and blue litmus paper is dipped in boiling water, the color of the litmus paper does not change. This proves that the water in the pot is relieving.

5.Describe the mitigation process with an example.

Answer:   The chemical reaction of acids and bases is called relief. This process produces salt and water .

6.  Mark the following sentences if they are correct (shu) and if they are incorrect (a).

(a) Nitric acid turns red litmus paper blue. (Shu/A)
 
Answer:  Oh

(b) Sodium hydroxide turns blue litmus red. (Shu/A) 

Answer:   Oh

(c) Sodium hydroxide and hydrochloric acid react with each other to form water and salts. (Shu/A)

Answer:  Shu

(d) An indicator is a substance that shows different colors in alkaline and acidic solutions. (shu/ a )
 
Answer:  Shu

e) Tooth decay is caused by the presence of alkalis. (shu/ a )

Answer:   Oh

7. 7. There are some bottles of soft drinks in the young man's restaurant. But unfortunately these do not have labels. He should supply these drinks according to the demand of the customers. One customer needs an acidic, another an alkaline and a third a soothing drink. How do you decide which drink to give to whom?

Answer:  The young man will decide which bottle of drink to give to whom.
    
1) The water that turns red litmus blue will be alkaline.
2)  The water that turns blue litmus red will be acidic.
3) Water that does not change the color of red litmus or blue litmus is called prasham.

8. 8. Explain the reason. 

(a) If you suffer from acidity, you will take antacid tablets.

Answer: When we suffer from acidity, we take antacid tablets - because they remove the effects of excess acid and prevent pain.

(b) Calamine solution is rubbed on the skin when bitten by insects.

Answer:  Calamine solution is rubbed on the skin when bitten by insects because the sting of insects contains formic acid. When insects bite, they inject this acid. The effect of the bite is gone.

c) Factory wastes are treated before discharge into reservoirs.

Answer:  Factory wastes are treated before being discharged into reservoirs. Because - factory waste contains acids. If these wastes are allowed to go directly into the wetland. Then it will destroy the fish, frogs and various animals in the water. Therefore, factory wastes are treated before being discharged into the reservoir.

9. 9. You are given three liquids. One is hydrochloric acid, the other is sodium hydroxide and the third is sugar solution. How do you identify these? You only have a garlic indicator.

FOR STUDENTS

10. 10. A blue litmus paper was dipped in a solution. The paper remained blue. Explain the nature of the solution.

FOR STUDENTS

11. 11. Read the following sentences.

 (a) Both acids and bases change the color of all the indicators. 

(b) If an indicator changes color in acid, it does not change color in base. 

 (c) If an indicator changes color in bases, it does not change color in acids.

(d) Color change in acids and bases depends on the type of indicator. 
Which of the following statements is correct? 

(i) All four    
(ii) 'A' and 'D'
(iii) 'B' and 'C' 
(iv) 'D' only.

Answer: (ii) 'A' and 'D'