RBSE Solutions for Class10 Science Chapter 1 Chemical Reactions and Equations

 

Chapter 1 Chemical Reactions and Equations

These are the solutions of chapter 1 chemical reactions and equations of class 10 science of RBSE (Rajasthan education board). These solutions have been prepared by experienced teachers.

If you are preparing for RBSE class 10 board exams, then these solutions of intext and end exercise questions will help you a lot.

These solutions cover a complete syllabus  and will let you solve homework and assignments in an easy way.

 

Board	RBSE
Subject	Science
Chapter	Chemical Reactions and Equations
No. of Intext questions	08
No. of End exercise questions	20
Prescribed book	NCERT Science

 

 

TEXT BOOK QUESTIONS:

Answers of questions of page 6

Q.1 Why should magnesium ribbon be cleaned before burning in air?

Ans.Magnesium ribbon reacts with atmospheric Oxygen and form a oxide layer of Magnesium oxide which  does not allow Magnesium to burn.

That’s why Magnesium ribbon should be cleaned before burning to remove the layer of Magnesium oxide [MgO].

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

(i)Hydrogen +Chloride→HydrogenChloride

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

(iii)Sodium +water→Sodium hydroxide+ Hydrogen

 

Ans. Balanced equations for the reactions are as follows:

(i)H₂ + Cl₂→2HCl

(ii)3BaCl₂+Al₂Cl₃→3BaSO₄+2AlCl₃

(iii)2Na+2H₂O→2NaOH+H₂

Q.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.

(ii)  Sodium hydroxide solution (in water) reacts with hydrochloric acid solution (in water) to produce sodium

chloride and water. 

Ans. Balanced chemical equations with state symbols for the reactions are as follows:

(i)BaCl_2(aq) +Na₂SO_4(aq)→BaSO_4(aq)+ NaCl_(aq)

(ii) NaOH_(aq)+HCl_(aq)→NaCl_(aq)+H₂O

Answers of questions of page 10

 

Q.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.

Ans.     

(i)In white washing the wall a solution of quick lime is used.so substance ‘X’ is quick lime and its formula is CaO.

(ii) Substance ‘X’ [CaO] reacts with water to form calcium hydroxide (slaked lime).

 

Q.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.  Water (H₂O) contains two parts hydrogen and one part oxygenduring electrolysis of water, on passing current water decomposes to form hydrogen and oxygen gases. The amountof hydrogen and oxygen produced during electrolysis of water is in a 2:1 ratio.

 

           Electrolysis

H₂O_(l)  ----------- →  2H_2(g) + O₂(g)

       In the above reaction, the balanced equation shows that during electrolysis of water 1 mole of oxygen gas and 2 moles of hydrogen gas are produced. That’s why, the amount of gas is double in one of the test tubes and it is hydrogen gas.

Answers of questions of page 13

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

Ans. Iron is more active element than copper. Copper sulphate (CuSO₄) solution is of blue colour, Iron (Fe) displaces copper from its compound copper sulphate (CuSO₄) and changes to iron sulphate (FeSO₄) which is green in colour. That’s why blue colour of copper sulphate solution changes.

Fe+CuSO₄→FeSO₄ +Cu

 

Q.2 Give an example of a double displacement reaction other than the one given in above activity 1.10

 

Ans. The other example of a double displacement reaction is – mixing of solutions of sodium carbonate and calcium chloride and in this reaction calcium carbonate and sodium chloride are formed.

Na₂CO_3(aq)+CaCl_2(aq)→CaCO_3(s)+2NaCl_(aq)

 

Q.3 Identify the substances oxidized and the substances reduced in the following reactions:

(i)4Na_(s)+ O_2(g) →2Na₂O_(s)

(ii)CuO_(s) +H₂→Cu+H₂O

      

Ans .   

(i).Sodium gains oxygen so it gets oxidized and on the other hand oxygen gets reduced.

(ii)Copper oxide is reduced to copper and hydrogen gets oxide to water.

Reaction	Substance oxidised	Substance reduced
(i) (ii)	Na H2	O2 CuO

 

Answers of EXERCISES questions

Q.1 Which of the statement about the reaction below are incorrect?

2PbO_(s)+C_(s) →2Pb_(s)+CO_2(g)

(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.

 

Correct Ans.      (i)   a and b.

 

Q.2 Fe₂O₃ +2Al→Al₂O₃+2Fe

  The above reaction is an example of

  (a)  Combination reaction

  (b)  Double displacement reaction

  (c)  Decomposition reaction

  (d)  Displacement reaction

 

Correct Ans.    (d)  Displacement reaction

 

Q.3 What happens when dilute hydrochloric acid is added to iron fillings? 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

 

 Correct Ans.  (a)  Hydrogen gas and iron chloride are produced.

Fe_(s)+dil. 2HCl_(aq)→FeCl_2(aq)+H₂↑

 

Q.4 What is a balanced chemical equation? Why should the chemical equation be balanced?

Ans. The total numbers of atoms of reactants and products are equal in a balanced chemical equation.

On the basis of the ‘ Law of Conservation of mass’ – Mass can  neither be created nor destroyed. So, the total mass of reactants should be equal to the total mass of the products. That’s why chemical equations should be balanced.

 

Q.5 Translate the following statements in to 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 aluminum sulphate to give aluminum chloride and precipitate of barium sulphate.

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

Ans.  First of all , find the reactants and products in the given statement.

(a) Following reactants and products are given in the statement

Reactants	Hydrogen and nitrogen
Products	Ammonia

 

       N_2(g)+H_2(g)→2NH_3(g)

(b) Following reactants and products are given in the statement

Reactants	Hydrogen sulphide and air (oxygen)
Products	Water and sulphur di oxide

 

         H₂S_(g)+3O_2(g)→2H₂O_(l)+SO_2(g)

(c) Following reactants and products are given in the statement

Reactants	Barium chloride and aluminium sulphate
Products	Barium sulphate and Ammonium chloride

 

          3BaCl_2(s)+Al₂(SO₄)_3(aq)    →3BaSO₄↓  + AlCl₃

(d) Following reactants and products are given in the statement

Reactants	Potassium and water
Products	Potassium hydroxide and hydrogen

 

        2K_(s)+2H₂O_(l)→2KOH_(l)+H_2(g)

 

Q.6 Balance the following chemical equations:

(i)HNO₃+Ca(OH)₂→Ca(NO₃)₂+H₂O

(ii)NaOH+H₂SO₄→Na₂SO4+H₂O

(iii)NaCl+AgNO₃→BaSO₄+HCl

(iv)BaCl₂+H₂SO₄→BaSO₄+HCl

 Answer – Following are the balanced chemical equations

(i)2HNO₃+Ca(OH)₂→Ca(NO₃)₂+2H₂O

(ii)2NaOH+H₂SO₄→Na₂SO4+2H₂O

(iii)NaCl+AgNO₃→BaSO₄+HCl

(iv)BaCl₂+H₂SO₄→BaSO₄+2HCl

 

 

Q.7 Write the balanced chemical equations for the following reactions:

(a)Calcium hydroxide +Carbon di oxide→ Calcium carbonate +water

(b)Zinc+ Silver nitrate →Zinc nitrate +Silver

(c) Aluminium+ Copper Chloride →Aluminium chloride +Copper

(d)Barium chloride +Potassium sulphate →Barium sulphate potassium chloride

 

Answer – Write the chemical formula of reactants and products then write the balanced chemical equation.

(a)

Reactants	Product
Calcium hydroxide – Ca(OH)2	Calcium carbonate - CaCO3
Carbon dioxide – CO2	Water – H2O

 

     Ca(OH)₂+CO₂ →CaCO₃    + H₂O

 

(b)

Reactants	Product
Zinc – Zn	Zinc nitrate – ZnNO3
Silver nitrate – AgNO3	Silver - Ag

         

      Zn +2AgNO₃ →ZnNO₃+2Ag

 

(c)

Reactants	Product
Aluminium - Al	Aluminium chloride- AlCl3
Copper chloride – CuCl2	Copper - Cu

 

       2Al+3CuCl₂ →2AlCl₃+3Cu

 

(d)

Reactants	Product
Barium chloride- BaCl2	Barium sulphate – BaSO4
Potassium sulphate – K2SO4	Potassium chloride - KCl

 

      BaCl₂+K₂SO₄  → BaSO₄  +2KCl

Q.8 Write the balanced chemical equations for the following reactions and identify the type of reaction:     

      

(a)Potassium bromide(aq)+Barium iodide(aq)→Potssium iodide(aq)+Barium bromide(aq)

(b)Zinc carbonate→(s)Zinc oxide(s)+Carbon dioxide(g)

(c) Hydrogen(g) +Chlorine(g) →Hydrogen chloride(g)

(d)Magnesium(s)+Hydrochloric acid(aq) →Magnesium chloride(aq)+Hydrogen(g)

 

Answer

(a)2KBr_(aq)+BaI_2(aq)  →2KI_(aq)BaBr_2(aq)

This is a double displacement reaction.

 

(b)ZnCO_3(s) →ZnO_(s)+CO_2(g)

This is a decomposition reaction.

(c)H_2(g)+Cl_2(g) →2HCl_(g)

This is a combination reaction.

(d)Mg_(s)+HCl_(aq) →MgCl_2(aq)+H_2(g)

This is a displacement reaction.

Q.9 What does one mean by exothermic and endothermic reactions? Give examples.

Ans.     

 Exothermic reaction- Chemical reaction in which energy is released in the form of heat is called exothermic reaction.

C + O₂ → CO₂ +395kJ

Endothermic reaction -Chemical reaction in which energy is absorbed or gained i is called exothermic reaction.

N₂ + O₂ +180.5kJ →2NO

 

Q.10   Why is respiration considered as an exothermic reaction? Explain.

Ans.   Energy is essential for different life process and this energy is obtained from the food that   we eat.

During digestion, large molecules of food are broken down into simpler substancessuch as glucose. Glucose combines with oxygen in the cells and in thisprocess energy is released. 

The name of this reaction is respiration. Since energy is released in the whole process, it is an exothermic process.

 C₆H₁₂O₆ +6O₂→6CO₂ + 6H₂O+ energy

Q.11  Why are decomposition reactions called opposite of combination reaction?Write equations for these reactions.

Ans.In a combination reaction two or more substances (elements and compounds) combine to form a single substance, whereas in a decomposition reaction one substance (compound) changes to two or more simpler substances (elements or compounds). That’s why; a decomposition reaction is called opposite of combination reaction.

 

Combination reaction

2H₂ + O₂→2H₂O

Decomposition reaction

     Electric current

2H₂O -----------→2H₂ + O₂

 

Q.12  Write one equation each for decomposition reactions where energy is supplied in the form of heat, light or electricity.

Ans.   For decomposition reaction, energy is required in the form of heat, light or electricity.

(i)Decomposition of lime stone (Calcium Carbonate) into lime (calcium oxide) and carbon dioxide is carried out by supplying heat. This is called thermal decomposition.

             heat

CaCO₃  ------→CaO +CO₂

(ii)Decomposition of silver bromide into silver and bromine takes place on exposure to light.This is called photolysis.

               light

2AgBr----------- →   2Ag Br

(iii)Decomposition of water in hydrogen and oxygen gases takes place by supplying electricity.This is called electrolysis.

           Electric current

H₂O_(l)   ----------- →  2H_2(g) + O₂(g)

 

 

Q.13 What is the difference between the displacement and double displacement reactions? Write equations for these reactions.

Ans. Displacement reaction-   more reactive element replaces a less reactive element froma compound.

Displacement reaction	Double displacement reaction
A more reactive element displaces a less reactive element from a compound.	There is a mutual exchange of ions between two compounds.
Zn+ CuSO4→ZnSO4+Cu	BaCl2+K2SO4→BaSO4 +2KCl

 

Q.14  In the refining of silver, the recovery of silver from silver nitrate solution involved displacement by copper metal. Write down the reaction involved.

Ans.  In the refining of silver from silver nitrate solution by copper metal, the reaction is as follows:

 

Cu+2AgNO_3(aq)→Cu(NO₃)_2(aq) +2Ag

Q.15  What do you mean by precipitation reaction? Explain giving examples.

Ans.  A reaction in which an insoluble solid substance is formed , it is called precipitate and the reaction  is called a precipitation reaction.

 

BaCl₂+Na₂SO₄→BaSO₄2NaCl

Q.16  Explain the following in terms of gain or loss of oxygen with two examples each:

       (a)  Oxidation          (b)  reduction    

Ans.     

Oxidation -  In this process addtion of oxygen to a substnace

C+O₂ →CO₂

2Mg+O₂ →2MgO

Reduction – In this process loss of oxygen from a substance

2H₂O →2H₂ +O₂

2MgO →2Mg +O₂

Q.17   A shiny brown coloured element ‘X’ on heating in air becomes black in colour. Name the element ‘X’ and the black coloured compound formed.

Ans.  When air is passed over heated copper powder, it reacts with oxygen of air to form copper (II) oxide which is of black colour.

 2Cu+O₂ →2CuO

Element ‘X’ is copper and black coloured compound is copper (II) oxide

Q.18  Why do we apply paint on iron articles?

Ans.  For rusting of iron articles, their open surface, oxygen and moisture are essentially required. Applying paint, surface is covered and moreover oxygen of air is not contact of surface of metal.   Iron articles get rusted when come in contact of air and moisture but whenthey are painted, thecontact of iron articles from moisture and air is cut off. Hence, rusting is prevented.

 

Q.19 Oil and fat containing food items are flushed with nitrogen. Why?

Ans. When food items kept open and unprotected for some time, they give unpleasant smell and taste of become rancid, this process is called rancidity.  This happens because of oxidation of food items. Nitrogen is an inert gas and does not easily react with these substances. That’s why bags used in packing food items are flushed with nitrogen gas to remove oxygen inside the pack.

 

Q.20  Explain the following terms with an example each:

       (a)  Corrosion          (b)  rancidity

Ans.  (a). Corrosion is defined as a process where materials, usually metals, deteriorate as a resultof a chemical reaction with air, moisture, chemicals, etc.

Eg. - In the presence of moisture, Iron reacts with oxygen to form hydrated iron oxide.

 4Fe+3O₂+nH₂O 2Fe₂O₃.nH₂O

This hydrated iron oxide is rust.

   (b). Rancidity- The process of oxidation of fats and oils containing food items and their smell and taste get changed, this process is known as rancidity. For example - The taste and smell of butter changes when kept for long.

 

 

We hope these RBSE class 10 science chapter 1 solutions will help you securing good marks in board exams.

Related Topics

Chapter	Chapter Name
1	Chemical Reactions and Equations
2	Acids, Bases and Salts
3	Metals and Non-metals
4	Carbon and its Compounds
5	Life Processes
6	Control and Coordination
7	How do Organisms Reproduce?
8	Heredity
9	Light – Reflection and Refraction
10	The Human Eye and the Colourful World
11	Electricity
12	Magnetic Effects of Electric Current
13	Our Environment