Chemical Reactions and Equations Important Questions

Class X Chemistry Chapter --1

Chemical Reactions and Equations Important Questions 

1. The respiration process during which glucose undergoes slow combustion by combining with oxygen in the cells of our body to produce energy, is a kind of:

 a. Exothermic process

 b. Endothermic process

 c. Reversible process

 d. Physical process

Answer. a. Exothermic process

2. A chemical reaction does not involve:

 a. Formation of new substances having entirely different properties than that of the  reactants

 b. Breaking of old chemical bonds and formation of new chemical bonds

 c. Rearrangement of the atoms of reactants to form new products

 d. Changing of the atoms of on element into those of another element to form new  products

Answer. d. Changing of the atoms of on element into those of another element to form new  products

3. One of the following processes does not involve a chemical reaction. That is:

 a. Melting of candle wax when heated

 b. Burning of candle wax when heated

 c. Digestion of food in our stomach

 d. Ripening of banana

Answer. a. Melting of candle wax when heated

4. The neutralization reaction between an acid and a base is a type of:

 a. Double displacement reaction

 b. Displacement reaction

 c. Addition reaction

 d. Decomposition reaction

Answer. a. Double displacement reaction

5. When a magnesium ribbon is burnt in air, the ash formed is

(a)  black

(b)  white

(c)  yellow

(d)  pink

6. Which option denotes a double displacement reaction?

(a) A + B + C

(b) A + B → C

(c) AC + BD → AD + BC

(d) AC + B → AB + C

7. Which among the following is (are) double displacement reaction(s)?

(t) Pb + CuCl → PbCl2 + Cu

(ii) Na2SO4 + BaCl2 → BaSO4 + 2NaCl

(iii) C + O2 → CO2

(iv) CH4 + 2O2 → CO2 + 2H2O

(a) (i) and (iv)

(b) (ii) only

(c) (i) and (ii)

(d) (iii) and (iv)

Ans:- (b) (ii) only

8. Combustion reactions are always

(a) Exothermic

(b) Endothermic

(c) Sometimes exothermic

(d) Both (a) and (b).

Ans:- (a) Exothermic

9. What type of chemical reactions take place when electricity is passed through water?

(a) Displacement

(b) Combination

(c) Decomposition

(d) Double displacement

Answer: c

10. The condition produced by aerial oxidation of fats and oils in foods marked by unpleasant smell and taste is called:

(a) antioxidation

(b) reduction

(c) rancidity

(d) corrosion

Answer: c

11. Pb + CuCl2 → PbCl2 + Cu

The above reaction is an example of:

(a) combination

(b) double displacement

(c) decomposition

(d) displacement

Answer: d

12. The formula of Ammonium phosphate is

(a) NH4PO4

(b) (NH4)2PO4

(c) (NH4)3PO4

(d) (NH4)3(PO4)2

Answer: c

13. Electrolysis of water is a decomposition reaction. The molar ratio of hydrogen and oxygen gases liberated during electrolysis of water is [NCERT Exemplar Problems]

(a) 1 : 1

(b) 2 : 1

(c) 4 : 1

(d) 1 : 2

Ans:- (b) 2 : 1

1. Which type of chemical reaction does the general chemical reaction                     A + BC → AC + B represent?

Ans) A + BC → AC + B represents chemical displacement reaction

2) Which type of chemical reaction does the general chemical reaction AB → A + B represent?

Ans) AB → A + B represent chemical decomposition reaction

3. Which substance is added to foods high in oil and fat to prevent rancidity?

Ans) Antioxidants are added to foods high in oil and fat to prevent rancidity. Antioxidants prevent oxidation of fats and oils.

4) List any two changes that take place when oily foods get oxidized?

Ans) The two prominent changes that takes place when oily foods get oxidized are

a) Bad taste

b) Unpleasant smell

5 . On what chemical law, balancing of chemical equation is based?

Ans) Balancing of a chemical equation is based on the law of conservation of mass.

 6. Why do we apply paint on iron articles?

Ans) Iron articles are painted to prevent them from rusting. Once an iron article is painted, the contact of iron articles from moisture and air is cut off thus preventing rusting.

7. Name a few chemical reactions taking place in our everyday life.

Ans) Photosynthesis, respiration, digestion, corrosion, combustion of fuel, formation of curd, rotting of food, etc.

8. What do you observe when a matchstick flame is brought near a test tube containing hydrogen gas?

Ans) When a matchstick flame is brought near a tube containing hydrogen gas, it burns with a pop sound.

9. Respiration is an ………….. reaction.

Answer: exothermic

10. Any reaction that produces a ………….. is called a precipitation reaction.

Answer: Precipitate

11. Oxidation is the gain of ………….. or loss of …………..

Answer: oxygen, hydrogen

12. In rusting of iron, reddish brown coating formed on iron is …………..

Answer: Fe2O3

13. The oxidation and reduction reaction are also called ………….. reactions.

Answer: redox

 14. A balanced chemical equation has equal masses of various elements in ___________ and ___________ .

Answer: reactants, products

15. State one basic difference between a physical change and a chemical change. [CBSE 2011]

Explanation: In physical change, no new substance is formed whereas in a chemical change a new substance(s) is/are formed.