CG SCERT Chhattisgarh State Board Class 7 Science (Science and Technology) Chapter 4 Acids, Bases and Salts Exercises Questions and Answers.
(1) Choose the correct answer –
Question 1.
The colour of phenolphthalein in as acidic medium is –
(a) Pink
(b) Red
(c) Orange
(d) Colourless
Answer:- (d) Colourless.
Question 2.
Formation of salt by the reaction of an acid with a base is called –
(a) Acidification
(b) Basification
(c) Dehydration
(d) Neutralization
Answer:- (d) Neutralization.
Question 3.
Gas used to extinguish fire in a fire extinguisher is –
(a) Oxygen
(b) Hydrogen
(c) Carbon dioxide
(d) Nitrogen
Answer:- (c) Carbon dioxide.
(4) The juice of raw Mango is –
(a) Acidic
(b) Basic
(c) Neutral
(d) None of these
Answer:- (a) Acidic.
(2) Fill in the blanks –
(1) Acid are — in test.
Answer:- Sour.
(2) Bases are —- to touch.
Answer:- Soapy.
(3) The nature of common salt solution is —-.
Answer:- Neutral.
(4) Water solution bases are called —-.
Answer:- Alkalies.
(3) Make appropriate connection –
|
(1) Soap solution |
(c) | (a) Indicator |
| (2) Sugar solution | (d) |
(b) Acidic substance |
|
(3) Litmus paper |
(a) | (c) basic substance |
| (4) Lemon juice | (b) |
(d) neutral substance |
(4) Indentify true & false statements from the following & rewrite the false statement after correcting them
(a) Lemon juice changes red litmus – false
Answer:- Lemon juice changes blue litmus to red
(b) bases red rough to touch – False
Answer:- Bases are soapy to touch
(c) The function of an antacid is to increase acidity in the
Answer:- Stomach – False
– The function of an antacid is neutralise acid of from our stomach
(d) Coating of utensite prevents them from burning in fire
Answer:- False – Coating of utensite prevents them from corrosion.
(5) What is acid?
Answer:- The substance which turn blue litmus paper to red know as an acid. Ex- H2SO4, HCl
(6) How will you differentiate between an acid & a base?
|
Acid |
Bases |
|
Acid turn blue litmus paper red. |
Base turn red litmus paper blue. |
|
Acid are sour in test |
Bases are bitter in test |
|
Acid solution remain colourless with phenolphthalein |
Base solution gives pink colour with phenolphthalein |
(7) What are salts? Explain the reaction by which they are formed?
Ans. Salts is a compound which formed by the neutralising reaction between acid & an alkali.
Reaction between acid & an alkali
HCl + NaoH -> Nacl + H2O
Acid + Alkali -> Salt + water
(8) Water are antacid? What is their function?
Answer:- The substance which neutralise extra acid from our stomach is called antacid.
- Antacid give relief from sour belches.
- Antacid give relief from acidity in the stomach.
(9) Write the common & chemical names of least three salt that we use in our daily life.
| Common Name | Chemical Name |
| (1) Baking soda | – Sodium bicarbonate/NaHCO3 |
| (2) Washing soda | – Sodium carbonate/Na2CO3 |
| (3) Common salt | – Sodium chloride/Nacl |
