Chemical Reactions and Equations Worksheet Class 5 Worksheet EVS

WORKSHEET - 1

Topic - 1: Chemical Reactions and Equations

Q.1. Which of the following is not a physical change? (1 Marks)  [NCERT Exemp.]
(a) Boiling of water to give water vapour 
(b) Melting of ice to give water 
(c) Dissolution of salt in water 
(d) Combustion of liquefied petroleum gas (LPG)
Ans. (d)
Solution. During combustion of liquefied petroleum gas (LPG), it forms CO2 and H2O.

Q.2. Read the given passage and answer the following questions.

The physical states of the reactants and products can be represented by using the symbols, (s) for solids, (l) for liquids, (g) for gases and (aq) for an aqueous solution along with their respective formulae. The word aqueous is written if the reactant or product is present as a solution in water. Precipitation can also be represented by using an arrow pointing downwards (↓) instead of using symbol (s). In the same way, the gaseous state of an evolved gas can be represented by using an arrow pointing upward direction (↑) instead of using symbol (g). The specific condition of the reaction like temperature, pressure, catalyst etc., is written above or below the arrow in the chemical equation.
(a) Write the balanced chemical equation with state symbols for the given reaction: Magnesium reacting with dilute sulphuric acid  [1 Marks]
(b) To indicate the presence of a gaseous reactant or product, we use _____ or ____ symbol.  (1 Marks)
(c) Complete the missing variable given as X and Y in the following reaction:   (1 Marks)

2Na (s) + 2H2O (l) → 2NaOH (X) + H2 (Y)
(d) Which of the following reactions is balanced?  (1 Marks)
(i) 2NaCl + 2H2O → 2NaOH + 2Cl2 + H2 
(ii) Ca(OH)2 + Cl2 → CaOCl2 + H2O
Ans. (a) Mg (s) + H2SO4 (aq) → MgSO4 (aq) + H2 ↑
(b) (g) or ↑
(c) X is (aq) and Y is (g)
(d) Reaction II is balanced.

Q.3. Which one is a chemical change–rusting of iron or melting of iron?  (1 Marks) [Board Term-I Set-11, 2011] 
Ans. Rusting of iron

Q.4. (a) Write two observations when lead nitrate is heated in a test tube.   (1 Marks)
(b) Name the type of reaction.  (1 Marks)
(c) Write a balanced chemical equation to represent the above reaction.  (1 Marks) [Board SQP, 2020]
Ans. (a) It turns yellow due to formation of lead oxide and reddish-brown fumes evolve.  
(b) Thermal decomposition reaction.
(c) (CBSE Marking Scheme, 2020) 

Q.5. Define a chemical reaction. State four observations which help us to determine that a chemical reaction has taken place. Write one example of each observation with a balanced chemical equation.  (5 Marks) [Board Term-I, 2016]
Ans. Process in which new substances with new properties are formed by the rearrangement of atoms.  
(i) Evolution of gas: The chemical reaction between zinc and dilute H2SO4.

Zn(s) + H2SO4(aq) → ZnSO4(aq) + H2(g) ↑
(ii) Change in colour: The chemical reaction between potassium iodide and lead nitrate.

Pb(NO3)2(aq) + 2KI(s) → 2KNO3(aq) + PbI2(s)

 Colourless                                           Yellow
(iii) Formation of precipitate: The chemical reaction between sulphuric acid and barium chloride.

BaCl2(aq) + H2SO4(aq) → 2HCl(aq) + BaSO4(s)

                                          White precipitate
(iv) Change in temperature: The chemical reaction between quicklime and water.

CaO(s) + H2O (l) → Ca(OH)2(aq) + Heat

WORKSHEET - 2

Q.1. Which one of the following processes involves chemical reactions?  (1 Marks) [NCERT Exemp.]
(a) Storing of oxygen gas under pressure in a gas cylinder 
(b) Liquefaction of air 
(c) Keeping petrol in a china dish in the open 
(d) Heating copper wire in presence of air at high temperature
Ans. (d)
Solution. Chemical changes involve formation of new compounds from one or more substances. On heating copper wire in the presence of air at high-temperature copper (II) oxide is formed.

Q.2. Assertion and Reason :
Directions: In the following questions, a statement of assertion (a) is followed by a statement of reason (R). Mark the correct choice as : 
(a) Both assertion (a) and reason (R) are true and reason (R) is the correct explanation of assertion (a). 
(b) Both assertion (a) and reason (R) are true but reason (R) is not the correct explanation of assertion (a). 
(c) Assertion (a) is true but reason (R) is false. 
(d) Assertion (a) is false but reason (R) is true.
(i) Assertion (A): Carbon dioxide turns lime water milky.
Reason (R): Carbon dioxide sullies the water.  (1 Marks)
(ii) Assertion (A): A chemical reaction becomes faster at higher temperatures.
Reason (R): At higher temperatures, molecular motion becomes more rapid.   (1 Marks)
(i) Ans. (c)
Solution. Carbon dioxide reacts with lime water (calcium hydroxide) to form milky precipitate of calcium carbonate.
(ii) Ans. (a)
Solution. Both A and R are true and R is the correct explanation of A. A chemical reaction becomes faster at higher temperatures because, at high temperature, the movement of particles is greater.

Q.3. Name and state the law which is kept in mind while we balance a chemical equation.  (1 Marks) [Board Term-I Set-21, 2011]
Ans. Law of conservation of mass: Mass can neither be created nor destroyed during a chemical reaction.

Q.4. What happens when quick lime is added to water?  (1 Marks) [Board Term-I Set-A1, 2011, 2010]
Ans. Quick lime reacts with water vigorously to produce slaked lime and a large amount of heat.

CaO(s) + H2O (l) → Ca(OH)2 + Heat

(Quick lime)            (Slaked lime)

Q.5. When a copper wire was left in silver nitrate solution for sometime, it was observed that the solution turned bluish green. 
(i) Explain the observation. 
(ii) Write the balanced chemical equation to represent the change taking place.   (3 Marks) [Board Term-I, 2016]
Ans. (i) Copper is more reactive than silver. Hence, when copper wire is dipped in silver nitrate solution, it displaces silver from AgNO3 solution forming copper nitrate which is bluish-green in colour.
(ii) Cu + 2AgNO3 → Cu(NO3)2 + 2Ag

                           (Copper (II)   (Silver): bluish-green) (CBSE Marking Scheme, 2016)

                                nitrate)

Q.6. 2 g of ferrous sulphate crystals are heated in a dry boiling tube. Answer the following :
(i) List any two observations. 
(ii) Name the type of chemical reaction taking place. 
(iii) Write the chemical equation of the reaction.  (3 Marks) [Board Term-I, 2016]
Ans. (i) Two observations are :
(a) Change in state and colour. 
(b) Evolution of gas  
(ii) Decomposition reaction
(iii)

Q.7. (i) Solution of a substance ‘X’ is used for testing carbon dioxide. Write the equation of the reaction of ‘X’ with carbon dioxide. 
(ii) How is ‘X’ obtained? Write chemical equations.  (3 Marks) [Board Term-I, 2015]
Ans. (i) Substance X-Calcium Hydroxide. 
Ca(OH)2(aq) + CO2(g) → CaCO3(s) + H2O(l)

                                           (White ppt.)
(ii) Calcium hydroxide is obtained by reaction of calcium oxide and water.  
CaO(s) + H2O(l) → Ca(OH)2(aq) + Heat

Q.8.  What happens when : 
(i) Dilute hydrochloric acid is added to solid sodium carbonate. 
(ii) Quicklime is treated with water. 
(iii) Sodium chloride solution is added to lead nitrate solution. 
Also, write the chemical equation in each case.   (3 Marks) [Board Term-I, 2014]
Ans. (i) Na2CO3(s) + 2HCl(aq) → 2NaCl(aq) + H2O(l) + CO2(g)
(ii) CaO(s)  + H2O(l) → Ca(OH)2(aq) + Heat
(iii) Pb(NO3)2(aq) + 2NaCl(aq) → PbCl2(s) + 2NaNO3(aq) (CBSE Marking Scheme, 2014)

WORKSHEET - 3

Topic - 2: Types of chemical Reactions, corrosion and Rancidity

Q.1. Which of the following reactions is an endothermic reaction? (1 Marks) [Board SQP, 2020] 
(a) Burning of coal. 
(b) Decomposition of vegetable matter into compost. 
(c) Process of respiration. 
(d) Decomposition of calcium carbonate to form quicklime and carbon dioxide.
Ans. (d)
Solution. The reactions which require energy in the form of heat, light or electricity to break reactants are called endothermic reactions.

Q.2. Read the given passage and answer the following questions.

In the following chemical reaction, ‘‘zinc oxide reacts with carbon to produce zinc metal and carbon monoxide.’’ 
ZnO + C → Zn + CO 
(a) The substance getting oxidized is ________ and the one getting reduced is ________.  (1 Marks)
(b) State the reason for choosing the substances in (a). (1 Marks)
(c) Name the type of reaction.  (1 Marks)
(d) Give another example of a similar type of reaction. (1 Marks)
Ans. (a) C is getting oxidized to CO, ZnO is getting reduced to Zn. 
(b) As carbon is gaining oxygen and ZnO is losing oxygen. 
(c) It is a redox reaction or oxidation and reduction reaction.  
(d) CuO + H2 → Cu + H2O

Q.3. Why is hydrogen peroxide kept in coloured bottles? (1 Marks) [Board Term-I Set-36, Set (A1), 2011, 2010]
Ans. Hydrogen peroxide decomposes into H2O and O2 in the presence of sunlight and hence to prevent decomposition, they are kept in coloured bottles


Q.4. 2 g of silver chloride is taken in a china dish, and the china dish is placed in sunlight for some time. What will be your observation in this case? Write the chemical reaction involved in the form of a balanced chemical equation. Identify the type of chemical reaction. (3 Marks) [Board Delhi, Set- I, 2019]
Ans. 

• White silver chloride turns grey in sunlight.

• 

• Decomposition reaction/Photolytic decomposition. (CBSE Marking Scheme, 2019)

Q.5. Identify the type of reactions taking place in each of the following cases and write the balanced chemical equation for the reactions. 
(a) Zinc reacts with silver nitrate to produce zinc nitrate and silver. 
(b) Potassium iodide reacts with lead nitrate to produce potassium nitrate and lead iodide.  (3 Marks) [CBSE Board Delhi, Set- I, 2019]
Ans. (a) Displacement reaction
Zn + 2AgNO3 → Zn (NO3)2 + 2Ag
(b) Double displacement reaction  
2KI + Pb(NO3)2 → PbI2 + 2KNO3  (CBSE Marking Scheme, 2019)

Q.6. (i) Define corrosion.
(ii) What is corrosion of iron called? 
(iii) How will you recognise the corrosion of silver? 
(iv) Why is iron corrosion a serious problem? 
(v) How can we prevent corrosion of iron?  (1 Marks) [Board Term-I Set-NS9SX1D, 2016] [NCERT 2017]
Ans. (i) Corrosion is a process in which metals are deteriorated by action of air, moisture, chemicals etc.  
(ii) Rusting.  
(iii) Silver - black, copper green.
(iv) It destroys car bodies, bridges, railing etc.  (Any two)
(v) By Painting, alloying, greasing etc.  (Any two)
Detailed Answer : 
(i) Corrosion is a process in which metals are deteriorated by action of air, moisture, chemicals etc.  
(ii) Corrosion of iron is called rusting. 
(iii) Silver turns black as it reacts with H2S present in air and forms a layer of Ag2S.  
(iv) Corrosion of iron is a serious problem because it leads to wastage of tonnes of iron every year and a lot of money is spent to repair or replace it.  
(v) The iron articles should be painted to prevent it from corrosion. (CBSE Marking Scheme, 2016)

WORKSHEET - 4

Q.1. The following reaction is an example of a
4NH3(g) + 5O2(g) → 4NO(g) + 6H2O(g)
(i) Displacement reaction 
(ii) Combination reaction 
(iii) Redox reaction 
(iv) Neutralisation reaction  (1 Marks) [NCERT Exemp.]
(a) (i) and (iv) 
(b) (ii) and (iii) 
(c) (i) and (iii) 
(d) (iii) and (iv)
Ans. (c)
Solution. The given reaction is a redox reaction because oxidation and reduction both take place simultaneously. Also, it is a displacement reaction because hydrogen of NH3 has been displaced by oxygen.

Q.2. Read the given passage and answer the following questions.
P, Q and R are 3 elements which undergo chemical reactions according to the following equations:
(i) P2O3 + 2Q → Q2O3 + 2P 
(ii) 3RSO4 + 2Q → Q2(SO4)3 + 3R 
(iii) 3RO + 2P → P2O3 + 3R
(a) Which element is most reactive? (1 Marks)
(b) Which element is least reactive? (1 Marks)
(c) The type of reactions is (1 Marks)
(i) Displacement reaction 
(ii) Combination reaction 
(iii) Neutralisation reaction 
(iv) Substitution reaction
(d) Define the reaction.  (1 Marks)
Ans. (a) Q, as it has replaced both P and R from their compounds  
(b) R, as it has been replaced by both P and Q
(c) (i) Displacement reaction 
(d) Displacement reaction is a type of reaction in which a more active element displaces a less reactive element from its compound. 

Q.3. N2 + 3H2 → 2NH3, name the type of reaction. (1 Marks) [Board Term-I Set-A2, 2010] [DDE, 2017]
Ans. It is a combination reaction.

Q.4. On heating blue coloured powder of copper (ii) nitrate in a boiling tube, black copper oxide, O2 and a brown gas X is formed. 
(a) Identify the type of reaction and the gas X.
(b) Write a balanced chemical equation of the reaction. 
(c) Write the pH range of aqueous solution of the gas X.  (3 Marks) [CBSE Outside Delhi, Set- III, 2019]
Ans. (a) Decomposition / Thermal decomposition,
The gas X is NO2 or (nitrogen dioxide)
(b)
(c) Range less than 7 (or 0------6.9pH)  (CBSE Marking Scheme, 2019)
Detailed Answer :  
(a) Type of reaction: Thermal decomposition reaction. The gas X is nitrogen dioxide.
(b) 2Cu(NO3)2(s) → 2CuO(s) + 4NO2(g) + O2(g)
Copper nitrate(II)        Black       Brown
(c) As oxides of non-metals are acidic in nature, aqueous solution of nitrogen dioxide will have a pH range between 0 and 7.  (CBSE Marking Scheme, 2019)

Q.5. During the reaction of some metals with dilute hydrochloric acid, the following observations were made by a change. 
(a) Silver does not show any change. 
(b) Some bubbles of a gas are seen when lead is reacted with the acid. 
(c) The reaction of sodium is found to be highly explosive. 
(d) The temperature of the reaction mixture rises when aluminium is added to the acid. 
Explain these observations giving appropriate reasons.  (3 Marks) [CBSE Outside Delhi, Set- III, 2019]
Ans. (a) Silver is placed below Hydrogen in reactivity series / among least reactive metal / Silver does not react with dil. Hydrochloric acid.
(b) Rate of reaction is slow / bubbles of Hydrogen gas are formed / lead lies above hydrogen in reactivity series.
(c) Sodium is highly reactive / reaction is highly exothermic, evolving Hydrogen gas, which catches fire.
(d) Reaction is exothermic
Detailed Answer :  
(a) As silver is less reactive, it does not react with dilute hydrochloric acid.  
(b) Bubbles are seen due to the evolution of hydrogen gas.
Pb(s) + 2HCl (aq) → PbCl2(aq) + H2(g)
(c) As sodium is highly reactive metal, it reacts with dilute hydrochloric acid vigorously with the evolution of heat.  
(d) The reaction between aluminium with dilute hydrochloric acid is exothermic; thus, the temperature of the mixture rises on the addition of aluminium. (CBSE Marking Scheme, 2019)

Q.6. (i) Define corrosion. What name is given to the corrosion of iron? 
(ii) Name the colour of coating formed on silver and copper articles, when exposed to air. 
(iii) List two damages caused by corrosion and suggest how corrosion can be prevented.  (5 Marks) [Board Term-I 2016]
Ans.  (i) Corrosion is a process in which metals are deteriorated by action of air, moisture, chemicals etc. Corrosion of iron is Rusting.  
(ii) Silver - black, copper - green.  
(iii) (a) Car bodies, bridges, railing etc. (Any two) 
(b) Painting, alloying, greasing etc.  (Any two)

WORKSHEET - 5

Q.1. Three beakers labelled as A, B and C, each containing 25 mL of water were taken. A small amount of NaOH, anhydrous CuSO4 and NaCl were added to the beakers A, B and C respectively. It was observed that there was an increase in the temperature of the solutions contained in beakers A and B, whereas, in case of beaker C, the temperature of the solution falls. Which one of the following statement(s) is (are) correct? 
(i) In beakers A and B, an exothermic process has occurred. 
(ii) In beakers A and B, an endothermic process has occurred. 
(iii) In beaker C, an exothermic process has occurred. 
(iv) In beaker C, an endothermic process has occurred. 
(a) (i) only 
(b) (ii) only 
(c) (i) and (iv) 
(d) (ii) and (iii) (1 Marks) [NCERT Exemp.]
Ans. (c)
Solution. In beakers A and B, heat is given out, so the temperature of the solution increases, hence it is an exothermic reaction while in beaker C, heat is absorbed from water, so temperature falls, hence it is an endothermic process.

Q.2. The following diagram displays a chemical reaction. Observe and answer the following questions:


(a) The type of chemical reaction that will take place is
(i)   Photochemical decomposition 
(ii)  Displacement reaction 
(iii) Reduction reaction 
(iv) Combination reaction   (1 Marks)
(b) What happens to the silver chloride? (1 Marks)
(c) Write the chemical equation of the reaction involved. (1 Marks)
(d) Mention one commercial use of this salt. (1 Marks)
Ans. (a) (i) Photochemical decomposition 
(b) White silver chloride changes to grey, as it decomposes to silver and chlorine in presence of sunlight. 
(c)
(d) Black and white photography. 

Q.3. Assertion and Reason: 
Directions: In the following questions, a statement of assertion (a) is followed by a statement of reason (R). Mark the correct choice as :
(a) Both assertion (a) and reason (R) are true and reason (R) is the correct explanation of assertion (a). 
(b) Both assertion (a) and reason (R) are true but reason (R) is not the correct explanation of assertion (a). 
(c) Assertion (a) is true but reason (R) is false. 
(d) Assertion ( a) is false but reason (R) is true. 
(i) Assertion (A): Sodium metal is stored under Kerosene.
Reason (R): Metallic sodium melts when exposed to air.   (1 Marks)
(ii) Assertion (A): To dilute sulphuric acid, acid is added to water and not water to acid.
Reason (R): Specific heat of water is quite large.
(i) Ans. (c) 
Solution. Sodium is a very reactive metal. It is kept in kerosene to prevent it from coming in contact with oxygen and moisture. If this happens, it will react with the moisture present in air and form sodium hydroxide. This is a strongly exothermic reaction, and a lot of heat is generated.
(ii) Ans. (a)
Solution. The mixing of water to acid is highly exothermic in nature. If water is added to acid it produces a very large amount of heat which can break the container and sometimes even causes burnings. So it is advised to add concentrated acid to water in a very slow manner.

Q.4. Decomposition reactions require energy either in the form of heat or light or electricity for breaking down the reactants. Write one equation each for decomposition reactions where energy is supplied in the form of heat, light and electricity.  (3 Marks) [Delhi/Outside Delhi, 2018]
Ans.


(or any other equation for above decomposition reaction.)
Note: No marks to be deducted if equations are not balanced.  (CBSE Marking Scheme, 2018) 

Q.5. In the reaction :
MnO2 + 4HCl → MnCl2 + 2H2O + Cl2
(a) Name the compound (i) oxidized, (ii) reduced. 
(b) Define oxidation and reduction on its basis. (3 Marks) [Compartment Set 1, 2, 3 , 2018]
Ans. (a) (i) HCl is oxidized.
(ii) MnO2 is reduced.
(b) (i) Oxidation: Gain of Oxygen or loss of Hydrogen.
(ii) Reduction: Gain of Hydrogen or loss of Oxygen. (CBSE Marking Scheme, 2018) 

WORKSHEET - 6

Q.1. A dilute ferrous sulphate solution was gradually added to the beaker containing acidified permanganate solution. The light purple colour of the solution fades and finally disappears. Which of the following is the correct explanation for the observation? 
(a) KMnO4 is an oxidizing agent, it oxidizes FeSO4. 
(b) FeSO4 acts as an oxidizing agent and oxidizes KMnO4. 
(c) The colour disappears due to dilution; no reaction is involved. 
(d) KMnO4 is an unstable compound and decomposes in presence of FeSO4 to a colourless compound.  (1 Mark) [NCERT Exemp.]
Ans. (a)
Solution. A dilute ferrous sulphate solution was gradually added to the beaker containing acidified permanganate solution. A permanganate solution is usually purple in colour. The light purple colour of the solution fades and finally disappears. This is because potassium permanganate (KMnO4) is relatively an unstable compound; it tends to decompose in the presence of ferrous sulphate (FeSO4). This changes the colour of the solution from purple to colourless. FeSO4 gets oxidised to Fe2(SO4)  as KMnO4 acts as a good oxidizing agent in an acidic medium.

Q.2. Why do silver articles become black after sometime, when exposed to air?  (1 Marks) [Board Term-I, 2011]
Ans. They get tarnished by reacting with atmospheric air to form silver sulphide.

Q.3. Give reason why do chips manufacturers usually flush bags of chips with gas such as nitrogen?  (1 Marks) [Board Term-I Set (12), 2011]
Ans. To prevent the oil and fats of the chips from being oxidized or become rancid.

Q.4. Balance the following chemical equations and state whether they are exothermic or endothermic :

(i) Na + H2O → NaOH + H2 

(ii) FeSO4 → Fe2O3 + SO2 + SO3  (3 Mark) [Board Term-I, 2016]
Ans. (i) 2Na + 2H2O → 2NaOH + H2 
It is an exothermic reaction. 
(ii)

It is an endothermic reaction.

Q.5. Name the term used to indicate the development of unpleasant smell and taste in fats and oils containing food due to oxidation. What are antioxidants? Why are they added to fat and oil containing food? (3 Marks) [Board Term-I, 2016]
Ans. Rancidity : Antioxidants are substances which prevent oxidation, actually are reducing agents. When added to food, the fats and oils present in the food do not get oxidized easily, hence do not turn rancid and remain good to eat for a longer time.  (CBSE Marking Scheme, 2016)

Q.6. Name two metals which do not corrode easily. Give an example in each of the following case to support that : 
(i) Corrosion of some metals is an advantage. 
(ii) Corrosion of a metal is a serious problem.   (3 Marks) [Board Term-I, 2016]
Ans. Gold and platinum :
(i) Corrosion of aluminium is useful. A protective layer of aluminium oxide is formed on the surface of the metal which renders the metal passive and prevents its further corrosion.  
(ii) Corrosion of iron is a serious problem. Every year a large amount of money is spent to replace damaged iron and steel structures. So, here, corrosion is a serious problem. (CBSE Marking Scheme, 2016)

Q.7. Identify the type of chemical reaction in the following statements and define each of them :
(i) Digestion of food in our body 
(ii) Rusting of iron 
(iii) Heating of manganese dioxide with aluminium powder. 
(iv) Blue colour of copper sulphate solution disappears when iron filings are added to it. 
(v) Dilute hydrochloric acid is added to sodium hydroxide solution to form sodium chloride and water.  (5 Marks) [Board Term-I, 2016]
Ans. (i) Decomposition Reaction: Carbohydrates are broken down to form glucose.  
(ii) Oxidation Reaction: When an iron object is left in moist air for a considerable time, it gets covered with a red-brown flaky substance called rust.  
(iii) Displacement reaction: More reactive metal displaces less reactive metal from its salt solution.  
(iv) Displacement reaction: More reactive metal displaces less reactive metal from its salt solution.  
(v) Double displacement reaction: Reaction in which two compounds react by an exchange of ions to form two new compounds.  (CBSE Marking Scheme, 2016)