NIOS Class 10 Science and Technology Chapter 1 Solution - Chemical Reaction and Equations

 Class X

 Chapter 1 – Chemical Reactions and Equations 

NIOS Class 10 Science & Technology Chapter 1 Solution

Board	NIOS
Class	10th  (Secondary)
Subject	Science and Technology (212)
Topic	Question Answer, Solution, Notes

Science

 Question

 1: A solution of a substance ‘X’ is used for white washing. 

(i) Name the substance ‘X’ and write its formula. 

(ii) Write the reaction of the substance ‘X’ named in (i) above with water. 

Answer 

 (i) The substance ‘X’ is calcium oxide. Its chemical formula is CaO. 

(ii) Calcium oxide reacts vigorously with water to form calcium hydroxide (slaked lime). 

Question 

2: Why is the amount of gas collected in one of the test tubes in Activity 1.7 double of the amount collected in the other? Name this gas. 

Answer 

Water (H2O) contains two parts hydrogen and one part oxygen. Therefore, the amount of hydrogen and oxygen produced during electrolysis of water is in a 2:1 ratio. During electrolysis, since hydrogen goes to one test tube and oxygen goes to another, the amount of gas collected in one of the test tubes is double of the amount collected in the other.  

Class X 

Chapter 1 – Chemical Reactions and Equations Science Question 

1: Why does the colour of copper sulphate solution change when an iron nail is dipped in it? 

Answer When an iron nail is placed in a copper sulphate solution, iron displaces copper from copper sulphate solution forming iron sulphate, which is green in colour. Therefore, the blue colour of copper sulphate solution fades and green colour appears. 

Question

 2: Give an example of a double displacement reaction other than the one given in Activity 1.10. 

Answer 

Sodium carbonate reacts with calcium chloride to form calcium carbonate and sodium chloride. In this reaction, sodium carbonate and calcium chloride exchange ions to form two new compounds. Hence, it is a double displacement reaction. Question 

3: Identify the substances that are oxidised and the substances that are reduced in the following reactions. 

(i)(ii) Answer  

(i) Sodium (Na) is oxidised as it gains oxygen and oxygen gets reduced.  

Question 

5: Why does the colour of copper sulphate solution change when an iron nail is dipped in it?

 Answer

 When an iron nail is placed in a copper sulphate solution, iron displaces copper from copper sulphate solution forming iron sulphate, which is green in colour. Therefore, the blue colour of copper sulphate solution fades and green colour appears. 

Question 

6: Give an example of a double displacement reaction other than the one given in Activity 1.10. 

Answer 

Sodium carbonate reacts with calcium chloride to form calcium carbonate and sodium chloride. In this reaction, sodium carbonate and calcium chloride exchange ions to form two new compounds. Hence, it is a double displacement reaction. 

Question 

7: Identify the substances that are oxidised and the substances that are reduced in the following reactions. 

(i)(ii) Answer  (i) Sodium (Na) is oxidised as it gains oxygen and oxygen gets reduced.  

(ii) Copper oxide (CuO) is reduced to copper (Cu) while hydrogen (H2) gets oxidised to water (H2O).  

Exercise solution Questions

 1: Which of the statements about the reaction below are  incorrect?

 (a) Lead is getting reduced. 

(b) Carbon dioxide is getting oxidised. 

(c) Carbon is getting oxidised. 

(d) Lead oxide is getting reduced.

 (i) (a) and (b) (ii) (a) and (c) (iii) (a), (b) and (c) (iv) all Answer  

(i)(a) and (b)

 Question

 2: The above reaction is an example of a 

(a) combination reaction. 

(b) double displacement reaction. 

(c) decomposition reaction. 

(d) displacement reaction. 

Answer  

(d) The given reaction is an example of a displacement reaction. 

Question 

3: What happens when dilute hydrochloric acid is added to iron filings?

 Tick the correct answer. 

(a) Hydrogen gas and iron chloride are produced. 

(b) Chlorine gas and iron hydroxide are produced.

(c) No reaction takes place. (d) Iron salt and water are produced.  

Answer 

 (a) Hydrogen gas and iron chloride are produced. The reaction is as follows: 

Question 

4: What is a balanced chemical equation? Why should chemical equations be balanced?

 Answer

 A reaction which has an equal number of atoms of all the elements on both sides of the chemical equation is called a balanced chemical equation. The law of conservation of mass states that mass can neither be created nor destroyed. Hence, in a chemical reaction, the total mass of reactants should be equal to the total mass of the products. It means that the total number of atoms of each element should be equal on both sides of a chemical equation. Hence, it is for this reason that chemical equations should be balanced. 

Question 

5: Translate the following statements into chemical equations and then balance them. 

(a) Hydrogen gas combines with nitrogen to form ammonia. 

(b) Hydrogen sulphide gas burns in air to give water and sulphur dioxide. 

(c) Barium chloride reacts with aluminium sulphate to give aluminium chloride and a precipitate of barium sulphate. 

(d) Potassium metal reacts with water to give potassium hydroxide and hydrogen gas. 

Answer