NCERT Exemplar Class 10 Science Chapter 1 Chemical Reactions And Equations
Chapter 1 Chemical Reaction And Equation NCERT Exemplar for class 10 Science
NCERT Exemplar Class 10 Science Chapter 1 Chemical Reactions and Equations will help you understand all the fundamentals of chemical reactions as well as their symbolic representation in terms of equations and symbols. Here, students will learn to recognise chemical changes, write equations, classify chemical reactions and basically list a few examples of chemical reactions.
Thus, to help students get a clear idea about the chapter and the topics, simply acad provide the free pdf to NCERT exemplar for class 10th Chapter 1 – Chemical Reactions and Equations here. The exemplar is prepared by subject experts and is designed to help students get the right answers to questions and have a thorough revision of the entire chapter in the precise time of preparation. The NCERT Exemplar act as a very useful study tool and will help students to perform well in the board exam.
Explore the journey to the chemical reactions by scrolling down below!
1. Which of the following is not a physical change?
(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)
Soln:
Answer is (d) Combustion of Liquefied Petroleum Gas (LPG)
Explanation:
Combustion is always a chemical change because a new compound is formed after burning and it is irreversible.
2. 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
(a) (i) and (iv)
(b) (ii) and (iii)
(c) (i) and (iii)
(d) (iii) and (iv)
Soln: (c) (i) and (iii)
Explanation:
The reaction provided is a mixture of displacement and redox reaction. Oxygen displaces hydrogen in the ammonia, making it a displacement reaction. Nitrogen gets oxidized and oxygen is reduced, resulting in a redox reaction.
3. Which of the following statements about the given reaction are correct?
3Fe(s) + 4H2O(g) → Fe3O4 (s) + 4H2 (g)
- Iron metal is getting oxidised
- Water is getting reduced
- Water is acting as a reducing agent
- Water is acting as an oxidising agent
(a) (i), (ii) and (iii)
(b) (iii) and (iv)
(c) (i), (ii) and (iv)
(d) (ii) and (iv)
Soln: (c) (i), (ii) and (iv)
Here, oxygen combines with water to get oxidised. Oxygen is removed from water hence, it is getting reduced. Water provides oxygen, and it acts as an oxidizing agent.
4. Which of the following are exothermic processes?
(i) The 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) (iii) and (iv)
Soln: (a) (i) and (ii)
Explanation:
The exothermic processes release an enormous amount of heat – Hence, heat energy is released when water reacts with quick lime and acid reacts with water.
5. 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 the 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, the exothermic process has occurred.
(ii) In beakers A and B, the endothermic process has occurred.
(iii) In beaker C exothermic process has occurred.
(iv) In beaker C endothermic process has occurred.
(a) (i) only
(b) (ii) only
(c) (i) and (iv)
(d) (ii) and (iii)
Soln:
Answer is (c) (i) and (iv)
Explanation:
Exothermic processes will increase the temperature whereas endothermic processes will decrease the temperature.
6. 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 oxidising agent, it oxidises FeSO4
(b) FeSO4 acts as an oxidising agent and oxidises KMnO4
(c) The colour disappears due to dilution; no reaction is involved
(d) KMnO4 is an unstable compound and decomposes in the presence of FeSO4 to a colourless compound.
Soln: (a) KMnO4 is an oxidising agent, it oxidises FeSO4
Explanation:
In this reaction, potassium permanganate (KMnO4) is an oxidizing agent.
The solution is coloured purple because of the KMnO4 and it eventually disappears when all the KMnO4 in the solution is utilized.
7. Which among the following is(are) double displacement reaction(s)?
(i) Pb + CuCl2 → PbCl2 + Cu
(ii) Na2 SO4 + BaCl2 → BaSO4 + 2NaCl
(iii) C + O2 → CO2
(iv) CH4 + 2O2 → CO2 + 2H2O
(a) (i) and (iv)
(b) (ii) only
(c) (i) and (ii)
(d) (iii) and (iv)
Soln:
The answer is (b) (ii) only
Explanation:
Here, Sodium and Barium are displaced from each other’s salts, hence it is a double displacement reaction.
8. Which among the following statement(s) is (are) true? Exposure of silver chloride to sunlight for a long duration turns grey due to
(i) the formation of silver by decomposition of silver chloride
(ii) sublimation of silver chloride
(iii) decomposition of chlorine gas from silver chloride
(iv) oxidation of silver chloride
(a) (i) only
(b) (i) and (iii)
(c) (ii) and (iii)
(d) (iv) only
Soln:
Answer is (a) (i) only
9. Solid calcium oxide reacts vigorously with water to form calcium hydroxide accompanied by the liberation of heat. This process is called slaking of lime. Calcium hydroxide dissolves in water to form its solution called lime water. Which among the following is (are) true about slaking of lime and the solution formed?
(i) It is an endothermic reaction
(ii) It is an exothermic reaction
(iii) The pH of the resulting solution will be more than seven
(iv) The pH of the resulting solution will be less than seven
(a) (i) and (ii)
(b) (ii) and (iii)
(c) (i) and (iv)
(d) (iii) and (iv)
Soln:
The answer is (b) (ii) and (iii)
Explanation:
When solid calcium oxide reacts vigorously with water, it forms calcium hydroxide, which is accompanied by the generation of heat. This event proves the reaction is exothermic. The pH of the solution will be more than 7 because oxides and hydroxides of metals are alkaline.
10. Barium chloride, on reacting with ammonium sulphate, forms barium sulphate and ammonium chloride. Which of the following correctly represents the type of reaction involved?
(i) Displacement reaction
(ii) Precipitation reaction
(iii) Combination reaction
(iv) Double displacement reaction
(a) (i) only
(b) (ii) only
(c) (iv) only
(d) (ii) and (iv)
Soln:
Answer is (d) (ii) and (iv)
Explanation:
Ammonium and barium are getting displaced from their respective salts. Hence this is a double displacement reaction. It is also called a precipitation reaction due to the formation of white precipitate of barium sulphate.
11. Electrolysis of water is a decomposition reaction. The mole ratio of hydrogen and oxygen gases liberated during electrolysis of water is
(a) 1:1
(b) 2:1
(c) 4:1
(d) 1:2
Soln:
Answer is (b) 2:1
Explanation:
1 Mole of water has 2 moles of Hydrogen and 1 mole of water. Hence mole ration between hydrogen and oxygen is 2:1.
12. Which of the following is(are) an endothermic process(es)?
(i) Dilution of sulphuric acid
(ii) Sublimation of dry ice
(iii) Condensation of water vapours
(iv) Evaporation of water
(a) (i) and (iii)
(b) (ii) only (c)
(iii) only
(d) (ii) and (iv)
Soln:
Answer is (d) (ii) and (iv)
Explanation:
Change of solid to gas or liquid to gas absorbs heat hence sublimation of dry ice and evaporation is an endothermic reaction.
13. In the double displacement reaction between aqueous potassium iodide and aqueous lead nitrate, a yellow precipitate of lead iodide is formed. While performing the activity, if lead nitrate is not available, which of the following can be used in place of lead nitrate?
(a) Lead sulphate (insoluble)
(b) Lead acetate
(c) Ammonium nitrate
(d) Potassium sulphate
Soln:
The answer is (b) Lead acetate
Explanation:
To get lead iodide we need a compound containing lead hence Ammonium nitrate and Potassium sulphate are ruled out. Lead sulphate is insoluble hence it cannot be used so the answer is (b) Lead acetate
14. Which of the following gases can be used for storage of fresh sample of an oil for a long time?
(a) Carbon dioxide or oxygen
(b) Nitrogen or oxygen
(c) Carbon dioxide or helium
(d) Helium or nitrogen
Soln:
The answer is (d) Helium or nitrogen
Explanation:
Oxygen cannot be used as it is an oxidizing agent. Helium can be used as it is an inert gas. Nitrogen is less reactive and it is cheaper than Helium. In most cases, nitrogen is used in packet to prevent rancidity.
15. The following reaction is used for the preparation of oxygen gas in the laboratory
2KClO3(s)HeatCatalyst2KCl(s)+3O2(g)
Which of the following statement(s) is(are) correct about the reaction?
(a) It is a decomposition reaction and endothermic in nature
(b) It is a combination reaction
(c) It is a decomposition reaction and accompanied by the release of heat
(d) It is a photochemical decomposition reaction and exothermic in nature
Soln:
Answer is (a) It is a decomposition reaction and endothermic in nature
Explanation:
Potassium chlorate decomposes to give potassium chloride and oxygen. This is a decomposition reaction which is endothermic in nature.
16. Which one of the following processes involves chemical reactions?
(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 the presence of air at high temperature
Soln:
The answer is (d) Heating copper wire in the presence of air at a high temperature
Explanation :
In first three options given here, there is no involvement of chemical reaction. When copper is heated in the presence of air at high-temperature copper undergoes oxidation reaction to give out copper oxide.
Short Answer Questions
19. Write the balanced chemical equations for the following reactions and identify the type of reaction in each case.
(a) Nitrogen gas is treated with hydrogen gas in the presence of a catalyst at 773K to form ammonia gas.
(b) Sodium hydroxide solution is treated with acetic acid to form sodium acetate and water.
(c) Ethanol is warmed with ethanoic acid to form ethyl acetate in the presence of concentrated H2 SO4.
(d) Ethene is burnt in the presence of oxygen to form carbon dioxide, water and releases heat and light.
N2(g)+3H2(g)= catalyst 773K2NH2(g)
Option (a) is a combination reaction.
(b)
NaOH(aq)+CH3COOH(aq)⟶CH3COONa(aq)+H2O(l)
Option (b) is a neutralisation reaction between a strong base and a weak acid.
(c)
C2H5OH(aq)+CH3COOH(l)⟶CH3COO C2H5(aq)+H2O(t)
Option (c) is a neutralisation reaction and double displacement reaction.
(d)
C2H4(g)+3O2(g)→2CO2(g)+2H2O(g)+ Heat + Light
Option (d) is an example of an oxidation reaction.
20. Write the balanced chemical equations for the following reactions and identify the type of reaction in each case.
(a) Thermite reaction, iron (III) oxide reacts with aluminium and gives molten iron and aluminium oxide.
(b) Magnesium ribbon is burnt in an atmosphere of nitrogen gas to form solid magnesium nitride.
(c) Chlorine gas is passed in an aqueous potassium iodide solution to form potassium chloride solution and solid iodine.
(d) Ethanol is burnt in air to form carbon dioxide, water and releases heat.
Soln:
(a) Thermit reaction, iron (III) oxide reacts with aluminium and gives molten iron and aluminium oxide.
FE2O3 + 2Al → Al2O3(s)+ 2Fe (l)
This is a Single displacement reaction
(b) Magnesium ribbon is burnt in an atmosphere of nitrogen gas to form solid magnesium nitride.
3 Mg(s)+ N2 → Mg3N2
The reaction is a Combination reaction
(c) Chlorine gas is passed in an aqueous potassium iodide solution to form potassium chloride solution and solid iodine.
Cl2(g)+2KI (aq) → 2KCl(Aq) +I2(s)
This is a Single displacement reaction
(d) Ethanol is burnt in air to form carbon dioxide, water and releases heat.
C2H5OH+ 3O2 → 2CO2+ 3H2O+ heat
This is a Combustion reaction
21. Complete the missing components/variables given as x and y in the following reactions
(a) Pb(NO3 ) 2 (aq) + 2KI(aq) → PbI2 (x) + 2KNO3 (y)
(b) Cu(s) + 2Ag NO3 (aq) → Cu(NO3 ) 2 (aq) + x(s)
(c) Zn(s) + H2 SO4 (aq) → ZnSO4 (x) + H2 (y)
(d) CaCO3 (s) →x CaO(s) + CO2 (g)
Soln:
(a) Pb(NO3 ) 2 (aq) + 2KI(aq) → PbI2 (s) + 2KNO3 (aq)
(b) Cu(s) + 2Ag NO3 (aq) → Cu(NO3 ) 2 (aq) + 2Ag(s)
(c) Zn(s) + H2 SO4 (aq) → ZnSO4 (aq) + H2 (g)
(d) CaCO3 (s) →heat→ CaO(s) + CO2 (g)
- x(s), y (aq)
- x is 2Ag
- x-(aq) y(g)
- x is heat
22. Which among the following changes are exothermic or endothermic in nature?
(a) Decomposition of ferrous sulphate
(b) Dilution of sulphuric acid
(c) Dissolution of sodium hydroxide in water
(d) Dissolution of ammonium chloride in water
Soln:
Exothermic reactions
(b) Dilution of sulphuric acid
(c) Dissolution of sodium hydroxide in water
Endothermic reaction
a) Decomposition of ferrous sulphate
(d) Dissolution of ammonium chloride in water
23. Identify the reducing agent in the following reactions
(a) 4NH3 + 5O2 → 4NO + 6H2O
(b) H2O + F2 → HF + HOF
(c) Fe2O3 + 3CO → 2Fe + 3CO2
(d) 2H2 + O2 → 2H2O
Soln:
- NH3-Ammonia
- H2O – Water
- CO-Carbon momnoxide
- H2- Hydrogen
24. Identify the oxidising agent (oxidant) in the following reactions
(a) Pb3O4 + 8HCl → 3PbCl2 + Cl2 + 4H2O
(b) 2Mg + O2 → 2MgO
(c) CuSO4 + Zn → Cu + ZnSO4
(d) V2O5 + 5Ca → 2V + 5CaO
(e) 3Fe + 4H2O → Fe3O4 + 4H2
(f) CuO + H2 → Cu + H2O
Soln:
- Pb3O4
- O2
- CuSO4
- V2O5
- H2O
- CuO
25. Write the balanced chemical equations for the following reactions
(a) Sodium carbonate on reaction with hydrochloric acid in equal molar concentrations gives sodium chloride and sodium hydrogen carbonate.
(b) Sodium hydrogen carbonate on reaction with hydrochloric acid gives sodium chloride, water and liberates carbon dioxide.
(c) Copper sulphate on treatment with potassium iodide precipitates cuprous iodide (Cu2 I2 ), liberates iodine gas and also forms potassium sulphate.
Soln:
(a) Na2CO3 + HCl → NaCl + NaHCO3
(b) NaHCO3 + HCl → NaCl + H2O + CO2
(c) 2CuSO4+4Kl →2K2SO4+CU2I2+I2
26. A solution of potassium chloride when mixed with silver nitrate solution, an insoluble white substance is formed. Write the chemical reaction involved and also mention the type of chemical reaction?
Soln:
KCl(aq) + AgNO3(aq) → AgCl(s) + KNO3(aq)
This is a double displacement and precipitation reaction.
27. Ferrous sulphate decomposes with the evolution of a gas having a characteristic odour of burning sulphur. Write the chemical reaction involved and identify the type of reaction.
Soln
2FeSO4=Fe2O3+SO2+SO3
This is a decomposition reaction.
28. Why do fireflies glow at night?
Soln:
Fireflies produce a chemical reaction inside their bodies which allows them to glow at night. Oxygen combines with calcium, ATP and luciferin in the presence of an enzyme called luciferase. This results in bioluminescence.
29. Grapes hanging on the plant do not ferment but after being plucked from the plant can be fermented. Under what conditions do these grapes ferment? Is it a chemical or a physical change?
Soln:
Grapes on the plant do not ferment because of the defence mechanism of plants. When grapes are plucked from the plant, grapes react with yeast to carry out fermentation. Here, sugar changes to alcohol and it is a chemical change.
30. Which among the following are physical or chemical changes?
(a) Evaporation of petrol
(b) Burning of Liquefied Petroleum Gas (LPG)
(c) Heating of an iron rod to red hot.
(d) Curdling of milk
(e) Sublimation of solid ammonium chloride
Soln:
Physical changes
- Evaporation of petrol
- Heating of an iron rod to red hot.
- Sublimation of solid ammonium chloride
Chemical changes
- Burning of Liquefied Petroleum Gas (LPG)
- (d) Curdling of milk
31. During the reaction of some metals with dilute hydrochloric acid, the following observations were made.
(a) Silver metal does not show any change
(b) The temperature of the reaction mixture rises when aluminium (Al) is added.
(c) The reaction of sodium metal is found to be highly explosive
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