1. Acids, Bases, and Salts.
2. Chemical properties acids and base.
3. How to acids and Bases react with metal.
4. Acids and Bases react with each other.
5. Reaction metallic Oxides with acids.
6. Reaction of non metallic Oxides with base.
7. What do all acids and all bases have in common.
8. What happens to an Acids or a Base in water solution.
9. How strong are acid or base solution.
10. Importance of pH in everyday life.
11. Family of salts
12. pH of salts
13. Chemicals from common salts
Questions - Answers
NCERT Textbook
Page No. 2.
Question:
You have been provided with three test tubes. One of them contains distilled water and the other two contain an acidic solution and a basic solution, respectively. If you are given only red litmus paper, how will you identify the contents of each test tube?
Answer
We dip the litmus paper one by one in each test tubes.
If there is no change in the colour of litmus paper we say that solutions can be either distilled water or acidic.
Now, we dip the litmus paper in the third test tube in which colour is changed and we clear that this is basic solution. Now, the colour of litmus paper becomes blue.
Now, we dip the litmus paper in other two test tubes. If colour is changed we say it is acidic otherwise distilled water.
In this process we identify the solutions of test tubes.
Page No.6.
Questions
1. Why should curd or sour substances not be kept in brass and copper vessel?
Answer:
The curd or sour substances are acidic. Copper and brass are matal and alloy of metal. When curd or sour substances reacts with metal displace hydrogen gas and form salt together with harmful products.
Acid + metal -> hydrogen + salt .
2HSO₄ + 2Cu -> 2CuSO₄ + H₂
Therefore, curd or sour subtances shoud not kept in brass and brass or copper vessel.
Q.No.2. Which gas is usually librated when an acid reacts with a metal? Illustrate with an example. How will you test for presence of this gas?
Answer :
Hydrogen gas is librated during the chemical reaction between acids and salts.
Example is given below
Zn + 2H₂SO₄ -> Zn(SO₄) + 2H₂.
We can test the evolved hydrogen gas by its burning with a pop sound when candle is brought near the gas.
Q.No.3. Metal compound A reacts with dilute hydrochloric acid to produce effervescence. The gas evolved extinguishes a burning candle. Write a balanced chemical equation for the reaction if one of the compound formed is calciumchloride.
Answer:
The balanced chemical equation is given below.
CaCO₃ + 2HCl -> CaCl₂ + CO₂ + H₂O
