CBSE Class 10 Science Chemical Reactions and Equations Assignment Set A

Read and download free pdf of CBSE Class 10 Science Chemical Reactions and Equations Assignment Set A. Get printable school Assignments for Class 10 Science. Standard 10 students should practise questions and answers given here for Chapter 1 Chemical Reactions And Equations Science in Grade 10 which will help them to strengthen their understanding of all important topics. Students should also download free pdf of Printable Worksheets for Class 10 Science prepared as per the latest books and syllabus issued by NCERT, CBSE, KVS and do problems daily to score better marks in tests and examinations

Assignment for Class 10 Science Chapter 1 Chemical Reactions And Equations

Class 10 Science students should refer to the following printable assignment in Pdf for Chapter 1 Chemical Reactions And Equations in standard 10. This test paper with questions and answers for Grade 10 Science will be very useful for exams and help you to score good marks

Chapter 1 Chemical Reactions And Equations Class 10 Science Assignment

Question. When ferrous sulphate is heated strongly it undergoes decomposition to form ferric oxide as a main product accompanied by a change in color from: 
(a) Blue to green.
(b) Green to blue.
(c) Green to brown.
(d) Green to yellow.

Answer : C

Question. In the equation, NaOH + HNO3 -> NaNO3 + H2O nitric acid is acting as 
(a) An oxidizing agent
(b) An acid
(c) A nitrating agent
(d) A dehydrating agent

Answer : B

Question. Select the oxidising agent for the following reaction: 
H2S + I2 > 2HI + S
(a) I2
(b) H2S
(C) HI
(d) S

Answer : A

Question. The Following Reaction Is An Example Of : 4NH3(G) + 5O2(G) → 4NO(G) + 6H2O(G) 
(a) Displacement reaction and Neutralisation reaction
(b) Combination reaction and Redox reaction
(c) Displacement reaction and Redox reaction
(d) Neutralisation reaction and Redox reaction

Answer : C

Question. A substance which oxidized itself and reduces other is known as 
(a) Oxidizing agent
(b) Reducing agent
(c) Both of these
(d) None of these

Answer : B

Question. Consider reaction: Al(s) + O₂ (g) → Al₂O₃. Moles of Al(s) needed to balance equation are 
(a) 1
(b) 2
(c) 3
(d) 4

Answer : D

Question. It is necessary to balance a chemical equation in order to satisfy the law of: 
(a) Conservation of motion
(b) Conservation of momentum
(c) Conservation of energy
(d) Conservation of mass

Answer : D

Question. Which of the following does show an oxidation reaction? 
(a) Gain of oxygen
(b) Loss of oxygen
(c) Gain of hydrogen
(d) None of the above

Answer : A

Question. MnO2 + 4HCl → 2 + 2H2O + Cl2 Identify the substance oxidized in the above equation. 
(a) MnCl2
(b) HCl
(c) H2O
(d) MnO2

Answer : D

Question. When crystals of lead nitrate are heated strongly in a dry test tube 
(a) crystals immediately melt
(b) a brown residue is left
(c) white fumes appear in the tube
(d) a yellow residue is left

Answer : B

Question. Which of the following is Not True with respect to the neutralisation reaction? 
(a) Salt is formed.
(b) Reaction occurs between an acid and a base.
(c) Reactive element displaces less reactive element.
(d) Reactants are in gaseous state.

Answer : D

Question. An element X on exposure to moist air turns reddish-brown and a new compound Y is formed. The substances X and Y are 
(a) X = Fe, Y = Fe₂O₃
(b) X = Ag, Y = Ag₂S
(c) X = Cu, Y = CuO
(d) X = Al, Y = Al₂O₃

Answer : A

Question. If magnesium is gently heated, it forms 
(a) Magnesium oxide
(b) Magnesium sulfide
(c) Magnesium nitrite
(d) Magnesium carbonate

Answer : A

Question. What chemicals are used in fireworks? 
(a) Copper chloride
(b) Calcium chloride
(c) Barium chloride
(d) All of above

Answer : D

Question. In a chemical reaction between sulphuric acid and barium chloride solution the white precipitates formed are of: 
(a) Hydrochloric acid
(b) Barium sulphate
(c) Chlorine
(d) Sulphur

Answer : B

Question. Color of Solid magnesium is 
(a) Dark grey
(b) Silver grey
(c) Black
(d) Whitish silver

Answer : B

Question. Consider equation: Cu⁺² (aq) + 2OH⁻(aq) → Cu(OH)₂ (s). precipitate of Copper Hydroxide (Cu(OH)₂) will be of 
(a) Green color
(b) Blue color
(c) Brown color
(d) White color

Answer : B

Question. Consider The Following Statements, Choose The Incorrect One(S): 
(a) The chemical equation is balance to satisfy the law of conservation of mass in chemical reaction.
(b) We should never change the formula of an element or compound to balance and equation.
(c) Those reaction in which heat is evolved are known as exothermic reactions.
(d) When Methane (CH4) burns in oxygen of air it forms carbon monoxide and water vapour.

Answer : D

Question. Which of the following reactions can also be termed as thermal decomposition reaction? 
(a) Combination Reaction
(b) Decomposition Reaction
(c) Displacement reaction
(d) Double displacement reaction

Answer : B

Question. What is the name of the process where fatty foods become rancid? 
(a) Corrosion
(b) Oxidation
(c) Reduction
(d) Hydrogenation

Answer : B

Question : State one basic difference between a physical change and a chemical change.
Answer :  In a physical change, no new substance is forme(d) In a chemical change, a new substance is forme(d)

Question :  Why eatables are preferably packed in aluminum foils?
Answer: Aluminum foils do not corrode in atmosphere even if kept for a long time. Actually, a protective coating of aluminum oxide (Al2O3) is formed on the surface of the metal. It stops any further reaction of the metal with air (oxygen) and water. The eatables do not get spoile(d)

Question : What happens when ZnCO3 is heated in the absence of air? Give the relevant equation.
Answer :  ZnO(s) and CO2(g)CO2(g) are forme(d) Chemical Equation:
                 ZnCO3 → ZnO + CO2

Question : What happens when an iron nail is put inside the copper sulfate solution? Write a reaction with observation.
Answer :  Iron nail turns brown, blue color of CuSO4 changes to colorless. (or light green)

Question :  You are given the following materials:
(i) Iron nails
(ii) Copper sulphate solution
(iii) Barium chloride solution
(iv) Copper powder
(v) Ferrous sulphate crystals
(vi) Quick lime.
Identify the type of chemical reaction taking place when :
(a) Barium chloride solution is mixed with copper sulphate solution and a white precipitate is observe(d)
(b) On heating, copper powder in air in a china dish, the surface of copper powder becomes black.
(c) On heating green ferrous sulphate crystals, reddish brown solid is left and a gas having smell of burning sulphur is notice(d)
(d) Iron nails when left dipped in blue copper sulphate solution become brownish in colour and blue colour of copper sulphate solution fades away.
(e) Quick lime reacts vigorously with water releasing a large amount of heat.

Question : Define a combination reaction. Give one example of a combination reaction which is also exothermi(c)
Answer :  A combination reaction is said to have occurred when two or more than two substances combine to form a single substance.

Question : Which of the following is a displacement reaction?


Answer: B

Question : Why do we store silver chloride in dark colored bottles? Explain in brief.
Answer :  Silver chloride on exposure to sunlight may decompose as per the following reaction
                     2AgCL → 2Ag + Cl2
Therefore it is stored in dark colored bottles.

Question : (i) Account for the following :
(a) White silver chloride turns grey in sunlight.
(b) Brown coloured copper powder on heating in air turns into black coloured substance.
(ii) What do you mean by
(a) Displacement reaction
(b) Reduction reaction
(c) Combination reaction?
Write balanced chemical equation in support for all
(i) (a) White coloured silver chloride undergoes decomposition in the presence of sunlight and forms silver (grey in colour) and chlorine.


(b) Brown coloured copper powder on heating in air gets oxidised to copper oxide which is black in colour.


(ii) For the different types of reactions,
(a) In a displacement reaction, one element takes the place of another in a compound dissolved in a solution. For example,
Fe(s) + CuSO4 (aq) ———> FeSO4 (aq) + Cu(s)
(b) Combination reaction may be defined as the reaction in which two or more substances combine under suitable conditions to form a new substance. For example,


(c) A decomposition reaction may be defined as the reaction in which a single substance decomposes or splits into two or more substances under suitable conditions.
For example,


It may be concluded that a certain substance is formed or synthesised in combination reaction and it breaks or splits in decomposition reaction. Therefore, the two reactions oppose each other. 

Question :  The colour of zinc metal is 
(a) Red dish brown
(b) silvery
(c) white
(d) Grey
Answer : D

Question : Which of the following are exothermic processes?
(i) Reaction of water with quick lime
(ii) Dilution of an acid
(iii) Evaporation of water
(iv) Sublimation of camphor (crystals)
(a) (i) and (ii)
(b) (ii) and (iii)
(c) (i) and (iv)
(d) (ii) and (iv)
Answer : A

Question : Find the incorrect statement : 
(I) Oxygen is highly combustible and hydrogen is supporter of combustion,
(II) Oxygen and hydrogen both are highly combustible,
(III) Oxygen and hydrogen both are supporters of combustion,
(IV) Hydrogen is highly combustible and oxygen is supporter of combustion
a. I, II and III
b. I, III and IV
c. IV, I and II
d. I, II and IV
Answer : A
Explanation: Only Hydrogen is combustible and Oxygen is a supporter of combustion
Question :  
Which of the following is correct conclusion? 
(a) Al is more reactive than Cu and Fe but less reactive than Zn
(b) Al is more reactive than Cu but less reactive than Zn and Fe
(c) Al is more reactive than Zn and Cu but less reactive than Fe
(d) Al is more reactive than Zn, Cu, Fe
Answer : D
Explanation: 2Al + 3ZnSO4 → Al2(SO4)3 + 3 Zn
2Al + 3CuSO4 → Al2(SO4)3 + 3 Cu
2Al + 3FeSO→ Al2(SO4)3 + 3Fe
Al is more reactive than Zn, Cu and Fe because it displaces them from their salt solution. 
Question : Four students A, B, C and D noted the initial colour of the solutions in beakers I, II, III and IV. After inserting zinc rods in each solution and leaving it undisturbed for two hours, noted the colour of each solution again.
They recorded their observations in the form of table given below:
Which student noted the colour change in all the four beakers correctly? 
a. C
b. A
c. B
d. D
Answer : A
Explanation: In I and II no reaction takes place, therefore. In III, green solution of FeSO4 will change to colourless due to formation of zinc sulphate.
Question : What happens when copper powder is heated ? 
Answer :  Copper is oxidised to copper oxide.It means addition of oxygen.
Oxygen is reduced to copper oxide. It means addition of metal i.e reduction.
So, balanced chemical equation is: 2Cu + O₂→ 2CuO
A black colour copper (II) oxide is forme(d) 
Question :  What does one mean by exothermic and endothermic reactions ? Give examples. 
Answer : Exothermic reaction: A chemical reaction in which heat is given out is known as exothermic reaction. For example
C(s) + O2 (g) → CO2(g) + Heat energy
NaOH (aq) + HCl(aq) → NaCl(aq) + H2O(l) + Heat energy
Endothermic reaction: A chemical reaction in which heat energy is absorbed is known as endothermic reaction. For example
Question :  There are different types of chemical reactions occurring around us or being carried out for the benefit of mankind, e.g. combination reactions, decomposition reactions, displacement reactions, precipitation reactions, reduction-oxidation (redox) reactions, photochemical reactions etc
Now answer the following questions:  
i. Combustion of coke is a combination reaction. CO2 is not a pollutant. Then why is combustion of coke harmful?
ii. Which reaction followed by two combination reactions are involved in white wash of walls?
iii. Give one use of tin plating in daily life.
iv. How photochemical reactions have played an important role in photography? 
Answer :  i. CO2 is not considered a pollutant up to a certain level. Rather, it helps in maintaining the temperature of the Earth. Combustion of coke is harmful as it increases the concentration of CO2 in the atmosphere which causes global warming due to the greenhouse effect.
ii. The reaction of calcium with oxygen gives quicklime (CaO) which when mixed with water forms slaked lime Ca(OH)2 [combination reaction] and when slaked lime is applied on walls then it reacts with CO2 of the air to form CaCO3.
iii. Tin-plating is preferred in the tiffin boxes because tin is non-poisonous and hence, does not contaminate the food kept in them. 
Question :. Why does the colour of heated copper powder becomes black when air is passed over it? 
Answer : When copper powder is heated in the presence of air,a black coating of copper oxide is formed. 
Question : Two beakers A and B contain Iron (II) sulphate solution. In the beaker A is placed a small piece of copper and in the beaker B is placed a small piece of zinc. It is found that a grey deposit forms on the zinc but not on the copper. What can be concluded from these observations? 
Answer : From these observation we can conclude that zinc is most active metal followed by iron and copper.
Copper does not react, but zinc reacts with ferrous sulphate solution. Thus, zinc is most reactive, followed by iron and copper.
Zn + FeSO4 +→ ZnSO4 + Fe
Cu + FeSO4 →No reaction 
Question : What are the types of combination reactions ? Give example of each type. 
Answer : Combination reactions: A combination reaction is one in which two or more reactants combine to form a single product. Combination reactions are again of three types.
Types of Combination reactions:
i. Combination reactions between elements.
ii. Combination reactions between compounds.
iii. Combination reactions between elements and compounds.
iv. Combination reactions between elements: In these reactions elements were combined to form a product.
Examples : Formation of calcium oxide by the combination elements calcium and oxygen.
2Ca + O2 →  2CaO
Formation of ammonia by the combination of elements nitrogen and hydrogen.
N2 + 3H2 → 2NH3
v. Combination reactions between compounds: In these reactions compounds were combined to form product.
Example: Reaction of calcium oxide in water to form calcium hydroxide
CaO + H2O → Ca(OH)2
vi. Combination reactions between elements and compounds: In these reactions elements and compounds combined to form product.
Example:Formation of sulphur trioxide by the combination of sulphur dioxide and oxygen.
2SO2 + O2 → 2SO3
Question : Write the balanced chemical equation for the following reaction and identify the type of reaction.
Zinc carbonate (s)→ Zinc oxide (s) + Carbon dioxide (g) 
Answer : Zinc carbonate (s)→ Zinc oxide (s) + Carbon dioxide (g)
ZnCO3(s) → ZnO(s) + CO2(g)
This is decomposition reaction.
Question : Write the formula and then balance the following equations. 
a. Chlorine + Sodium hydroxide →Sodium chloride + Sodium chlorate + water
b. Iron sulphate + Hydrochloric acid → Iron chloride + Hydrogen sulphide
c. Calcium + Water  →Calcium hydroxide + Hydrogen
d. Zinc carbonate → Zinc oxide + Carbon dioxide
Answer : The formula and balance equations are as follows:
a. Chlorine + Sodium hydroxide →Sodium chloride + Sodium chlorate + water
3Cl2 + 6NaOH →5NaCl + NaClO3 + 3H2O
b. Iron sulphate + Hydrochloric →acid Iron chloride + Hydrogen sulphide
FeS + 2HCl →FeCl2 + H2S
c. Calcium + Water →Calcium hydroxide + Hydrogen
Ca + 2H2O →Ca(OH)2 + H2 
d. Zinc carbonate → Zinc oxide + Carbon dioxide
ZnCO3 →ZnO + CO2
e. Sodim nitrate + Sulphuric acid (conc.) →Sodium Sulphate + Nitric acid
2NaNO3 + H2SO4 →Na2SO4 + 2HNO3 
Question : Define corrosion. 
Answer : When a material reacts with the external environment, over a time, its structure will be deteriorated, and breaks down into small pieces. Ultimately, it can disintegrate into the atomic level. This is known as corrosion. Most commonly this happens to metals.
It is the slow eating up of the metals by the action of air and moisture of their surfaces. 
Question : Write the balanced chemical equations for the following reactions and identify the type of reaction in each case. 
i. In thermite reaction, iron (III) oxide reacts with aluminium and gives molten iron and aluminium oxide.
ii. Magnesium ribbon is burnt in an atmosphere of nitrogen gas to form solid magnesium nitride.  
Answer : 
The thermite reaction is a displacement reaction.
The formation of magnesium nitride as above is a combination reaction.

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