NCERT Chapter 1 Science Class 10 Adiitional SOLUTION || Ncert chapter 1 Solution class 10 || Chemistry || Science ||

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                                 Page 6:
Ques 1: Why should a magnesium ribbon be cleaned before burning in air?

Ans 1: Magnesium is very reactive metal like (Na, C a, etc.). When it expose to air it reacts with oxygen to form a layer magnesium oxide (Mg O) on its surface. 

                Mg + O 2→ 2 Mg O

This layer of magnesium oxide is quite stable and prevents further reaction of magnesium with oxygen. The magnesium ribbon is cleaned by sand paper to remove this layer so that the underlying metal can be used for the reaction.

Ques 2: Write the balanced equation for the following chemical reactions. 

(i) Hydrogen + Chlorine → Hydrogen chloride

(i i) Barium chloride + Aluminium sulphate → Barium sulphate + Aluminium chloride 

(i i i) Sodium + Water → Sodium hydroxide + Hydrogen

Ans 2: (i) H 2  + Cl 2 →2 H 

(i i) B a Cl 2 + Al 2 (SO 4) 3 →3 B a SO 4 + 2 Al Cl 3

(i i i) Na + H 2 O → Na OH

Ques 3: Write a balanced chemical equation with state symbols for the following reactions. 

(i) Solutions of barium chloride and sodium sulphate in water react to give insoluble barium sulphate and the solution of sodium chloride. 

(i i) Sodium hydroxide solution (in water) reacts with hydrochloric acid solution (in water) to produce sodium chloride solution and water.

Ans 3: (i) B a Cl 2 + Na 2 SO 4 → B a SO 4 + 2 Na Cl 

(i i) Na OH + H Cl → Na Cl + H 2 O

                               
                            Page 10:
Ques 1: A solution of a substance ‘X’ is used for white washing. 

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

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

Ans 1: (i). The substance ‘X’ is calcium oxide. Its chemical formula is Ca O. 

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

Ques 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. 

Ans 2: During the Electrolysis of water, hydrogen and oxygen is get separated by the  electricity. Water (H2O) contains two parts hydrogen and one part oxygen. 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.

                             
                               Page 13

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

Ans 1: When an iron nail is dipped in a copper sulphate solution, iron (which is more  reactive than copper) displaces copper from copper sulphate solution forming  iron sulphate, which is green in colour.

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

Ans 2: Sodium carbonate reacts with calcium chloride to form calcium carbonate and  sodium chloride.

   Na 2 CO 3 + C a  Cl 2 → C a CO 3 + 2 Na Cl

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

(i) 4Na(s) + O2(g) → 2Na2O(s)

(i i) Cu O(s) + H2(g) → Cu(s) + H2O(l)

Ans 3: (i). Sodium (Na) is oxidised as it gains oxygen and oxygen gets reduced. 

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

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