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. Before solving these questions, you can revise the chapter from Quick Revision Notes and practice with MCQs for better understanding.
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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 |
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)BaCl2(aq) +Na2SO4(aq)→BaSO4(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 thesubstance ‘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 oxygen during electrolysis of water, on passing current water decomposes to form hydrogen and oxygen gases. The amount of hydrogen and oxygen produced during electrolysis of water is in a 2:1 ratio.
Electrolysis
H2O(l) ———– → 2H2(g) + O2(g)
Inthe 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.
Na2CO3(aq)+CaCl2(aq)→CaCO3(s)+2NaCl(aq)
Q.3 Identify the substances oxidized and the substances reduced in the following reactions:
(i)4Na(s)+ O2(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 |
Substance |
|
(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)+CO2(g)
(a) Lead is gettingreduced.
(b) Carbon dioxide isgetting oxidised.
(c) Carbon is gettingoxidised.
(d) Lead oxide isgetting 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) Combinationreaction
(b) Double displacementreaction
(c) Decompositionreaction
(d) Displacementreaction
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)→FeCl2(aq)+H2↑
Q.4 What is a balanced chemical equation? Why should the chemical equation be balanced?
Ans. Thetotal 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 |
|
Products |
Ammonia |
N2(g)+H2(g)→2NH3(g)
(b) Following reactants and products are given in the statement
|
Reactants |
Hydrogen |
|
Products |
Water |
H2S(g)+3O2(g)→2H2O(l)+SO2(g)
(c) Following reactants and products are given in the statement
|
Reactants |
Barium |
|
Products |
Barium |
3BaCl2(s)+Al2(SO4)3(aq) →3BaSO4↓ + AlCl3
(d) Following reactants and products are given in the statement
|
Reactants |
Potassium |
|
Products |
Potassium |
2K(s)+2H2O(l)→2KOH(l)+H2(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 |
Calcium |
|
Carbon |
Water |
Ca(OH)2+CO2 →CaCO3 + H2O
(b)
|
Reactants |
Product |
|
Zinc – |
Zinc nitrate |
|
Silver |
Silver |
Zn +2AgNO3 →ZnNO3+2Ag
(c)
|
Reactants |
Product |
|
Aluminium |
Aluminium |
|
Copper |
Copper |
2Al+3CuCl2 →2AlCl3+3Cu
(d)
|
Reactants |
Product |
|
Barium |
Barium |
|
Potassium |
Potassium |
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)+BaI2(aq) →2KI(aq)BaBr2(aq)
This is a double displacement reaction.
(b)ZnCO3(s) →ZnO(s)+CO2(g)
This is a decomposition reaction.
(c)H2(g)+Cl2(g) →2HCl(g)
This is a combination reaction.
(d)Mg(s)+HCl(aq) →MgCl2(aq)+H2(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
Electriccurrent
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) ———– → 2H2(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 from a compound.
|
Displacement |
Double displacement reaction |
|
A more |
There |
|
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+2AgNO3(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 addition of oxygen to a substance
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 result of 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.