Do you know why iron turns reddish brown after some time, how food is digested in our body, and how plants make food using water, sunlight, and carbon dioxide? The answer to all these questions lies in Chemical Reactions and Equation Chapter 1 NCERT Exemplar. It is a process in which one or more substances react to form entirely new substances with different properties and composition. From burning of woods to digestion of food these chemical reactions occur everywhere around us. NCERT Solutions for Class 10 Science Chapter 1 Chemical Reactions and Equations helps students to understand all these interesting facts clearly.
This Story also Contains
These NCERT Exemplar solutions for class 10 Science present systematic explanations of chemical reactions and equations that form the basis of chemistry-based transformations, undergoing various chemical changes. These NCERT Exemplar solutions for Class 10 Science Chapter 1 covers easy-to-complex reactions and their practical applications in the real world. In this article, higher order thinking skills (HOTs) are also added to enhance your understanding of the concepts. These NCERT exemplar solutions follow the CBSE 2025 syllabus to properly train students for their board exams and their performances in competitive examinations.
At first, the MCQ questions are covered in the Class 10 Science NCERT Exemplar Solutions Chapter 1 Chemical Reactions and Equations to enhance your knowledge. The concepts are explained in detail in notes available on our website. Students can also check NCERT Solutions to all questions chapter-wise.
Law Admissions 2026 Open | Avail Merit-Based Scholarships
BBA/MBA/PGDM Early Bird Applications Deadline 06th Nov'26. Apply now using coupon code CAREER250 and get ₹250 off the application fee
Question 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)
Answer:
The correct answer is (d)
(a) Boiling of water to give water vapour – Change in state – Physical changeQuestion 2. The following reaction is an example of a:
$4NH_3 (g) + 5O_2(g)\rightarrow 4NO(g) + 6H_2O(g)$
(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)
Answer:
The correct answer is (c)
$4NH_3 (g) + 5O_2(g)\rightarrow 4NO(g) + 6H_2O(g)$Question 3. Which of the following statements about the given reaction are correct?
$3Fe(s) + 4H_2O(g)\rightarrow Fe_3O_4(s) + 4H_2(g)$
(i) Iron metal is getting oxidised
(ii) Water is getting reduced
(iii) Water is acting as reducing agent
(iv) Water is acting as oxidising agent
(a) (i), (ii) and (iii) (b) (iii) and (iv)
(c) (i), (ii) and (iv) (d) (ii) and (iv)
Answer:
The correct answer is (c)
$3Fe(s) + 4H_2O(g)\rightarrow Fe_3O_4(s) + 4H_2(g)$Question 4. 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) (iii) and (iv)
Answer:
The correct answer is (a)
When water reacts with water and acid it releases enormous amount of heat. Similarly, when water reacts with quick lime it releases a lot of heat.Question 5. Three beakers labelled as A, B and C each containing 25 mL of water were taken. A small amount of NaOH, anhydrous $CuSO_{4}$ 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, exothermic process has occurred.
(ii) In beakers A and B, 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)
Answer:
The correct answer is (c)
In beaker A:Question 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) $KMnO_{4}$ is an oxidising agent, it oxidises $FeSO_{4}$
(b)$FeSO_{4}$ acts as an oxidising agent and oxidises $KMnO_{4}$
(c) The colour disappears due to dilution; no reaction is involved
(d) $KMnO_{4}$ is an unstable compound and decomposes in presence of $FeSO_{4}$ to a colourless compound.
Answer:
The correct answer is (a)
$FeSO_4 +KMnO_{4}+H_{2}SO_{4}\rightarrow Fe_{2}(SO_{4})_{3}+MnSO_4+K_{2}SO_{4}+H_{2}O$Question 7. Which among the following is(are) double displacement reaction(s)?
(i) $Pb + CuCl_2 \rightarrow PbCl_2 + Cu$
(ii) $Na_2SO_4 + BaCl_2\rightarrow BaSO_4 + 2NaCl$
(iii) $C + O_2\rightarrow CO_2$
(iv) $CH_4 + 2O_2 \rightarrow CO_2 + 2H_2O$
(a) (i) and (iv) (b) (ii) only
(c) (i) and (ii) (d) (iii) and (iv)
Answer:
The correct answer is (b)
Double displacement reactions are those in which ions of the reactants are exchanged to form new compounds as products.Question 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
Answer:
The correct answer is (a)
$2AgCl\overset{light}{\rightarrow}2Ag +Cl_{2}$Question 9. Solid calcium oxide reacts vigorously with water to form calcium hydroxide accompanied by 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)
Answer:
The correct answer is (b)
$CaO + H_2O \rightarrow Ca(OH)_2 + heat$Question 10. Barium chloride on reacting with ammonium sulphate forms barium sulphate and ammonium chloride. Which of the following correctly represents the type of the 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)
Answer:
The correct answer is (d)
$BaCl_{2}+(NH_{4})_{2}SO_{4}\rightarrow BaSO_{4}+2NH_{4}Cl$Question 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
Answer:
The correct answer is (b)
The reaction is shown as:Question 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)
Answer:
The correct answer is (d)
Dilution of sulphuric acid with water is a highly exothermic process as it occurs with the evolution of heat.Question 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
Answer:
The correct answer is (b)
$2KI (aq)+Pb(NO_{3})_{2}(aq)\rightarrow PbI_{2}(s)+2KNO_{3}$Question 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
Answer:
The correct answer is (d)
Helium can be used as it is an inert gas. Nitrogen is less reactive and it is cheaper than Helium.Question 15. The following reaction is used for the preparation of oxygen gas in the laboratory
$2KClO_{3}(s) \xrightarrow[catalyst]{heat}2KCl(s)+3O_{2}(g)$
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 release of heat
(d) It is a photochemical decomposition reaction and exothermic in nature
Answer:
The correct answer is (a)
Potassium chlorate decomposes to give potassium chloride and oxygen. This is a decomposition reactionQuestion 16. Which one of the following processes involve 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 presence of air at high temperature
Answer:
The correct answer is (d)
Storing of oxygen gas under pressure in a gas cylinder – does not involve chemical reactionsQuestion 17. In which of the following chemical equations, the abbreviations represent the correct states of the reactants and products involved at reaction temperature?
(a) $2H_2 (l) + O_2 (l) \rightarrow 2H_2O (g)$
(b) $2H_2 (g) + O_2 (l)\rightarrow 2H_2O (l)$
(c) $2H_2 (g) + O_2 (g)\rightarrow 2H_2O (l)$
(d) $2H_2 (g) + O_2 (g)\rightarrow 2H_2O (g)$
Answer:
The correct answer is (c)
At room temperature hydrogen and oxygen are gases while water is liquid in nature hence option (c) represents correct states of reactants and products.Question 18. Which of the following are combination reactions?
(i)$2KClO_3\overset{heat}{\rightarrow} 2KCl + 3O_2$
(ii)$MgO + H_2O\rightarrow Mg(OH)_2$
(iii) $4Al + 3O_2\rightarrow 2Al_2O_3$
(iv) $Zn + FeSO_4\rightarrow ZnSO_4 + Fe$
(a) (i) and (iii) (b) (iii) and (iv)
(c) (ii) and (iv) (d) (ii) and (iii)
Answer:
The correct answer is (d)
A combination reaction is a reaction where two or more elements or compounds combine to form a single compound.
(i) )$2KClO_3\overset{heat}{\rightarrow} 2KCl + 3O_2$
Decomposition reaction.
(ii)$MgO + H_2O\rightarrow Mg(OH)_2$
Combination reaction as magnesium oxide and water combine to form magnesium hydroxide
(iii) $4Al + 3O_2\rightarrow 2Al_2O_3$
Combination reaction as aluminium combines with oxygen to form aluminium oxide
(iv)$Zn + FeSO_4\rightarrow ZnSO_4 + Fe$
Displacement reaction.
Question 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 $H_2SO_4 .$
(d) Ethene is burnt in the presence of oxygen to form carbon dioxide, water and releases heat and light.
Answer:
Chemical Reactions and EquationsQuestion 20. Write the balanced chemical equations for the following reactions and identify the type of reaction in each case.
(a) Thermit 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.
Answer:
(a) Thermit reaction, iron (III) oxide reacts with aluminum and gives molten iron and aluminum oxide.Question 21. Complete the missing components/variables given as x and y in the following reactions
(a) $Pb(NO_3)_2 (aq) + 2KI(aq) \rightarrow PbI_2 (x) + 2KNO_3(y)$
(b) $Cu(s) + 2AgNO_3(aq) \rightarrow Cu(NO_3)_2(aq) + x(s)$
(c) $Zn(s) + H_2SO_4(aq) \rightarrow ZnSO_4(x) + H_2(y)$
(d) $CaCO_3(s) \overset{x}{\rightarrow} CaO(s) + CO_2(g)$
Answer:
a) x (s), y (aq)Question 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
Answer:
(a) Decomposition of ferrous sulphateQuestion 23. Identify the reducing agent in the following reactions
(a) $4NH_3 + 5O_2\rightarrow 4NO + 6H_2O$
(b) $H_2O + F_2 \rightarrow HF + HOF$
(c) $Fe_2O_3 + 3CO \rightarrow 2Fe + 3CO_2$
(d) $2H_2 + O_2 \rightarrow 2H_2O$
Answer:
Reducing agent is the one which reduces other substance (by removal of oxygen or addition of hydrogen) and itself gets oxidised.Question 24. Identify the oxidising agent (oxidant) in the following reactions
(a) $Pb_3O_4 + 8HCl \rightarrow 3PbCl_2 + Cl_2 + 4H_2O$
(b) $2Mg + O_2 \rightarrow 2MgO$
(c) $CuSO_4 + Zn \rightarrow Cu + ZnSO_4$
(d) $V_2O_5 + 5Ca \rightarrow 2V + 5CaO$
(e) $3Fe + 4H_2O \rightarrow Fe_3O_4 + 4H_2$
(f) $CuO + H_2\rightarrow Cu + H_2O$
Answer:
An oxidizing agent is a reactant that removes electrons from other reactants during a redox reaction. The oxidizing agent typically takes these electrons for itself, thus gaining electrons and being reduced.Question25. 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 hydrogencarbonate.
(b) Sodium hydrogencarbonate on reaction with hydrochloric acid gives sodium chloride, water and liberates carbon dioxide.
(c) Copper sulphate on treatment with potassium iodide precipitates cuprous iodide $(Cu_2I_2)$, liberates iodine gas and also forms potassium sulphate.
Answer:
(a) $Na_2CO_3 + HCl \rightarrow NaCl + NaHCO_3$Answer:
$KCl(aq) + AgNO_3(aq) \rightarrow AgCl(s) + KNO_3(aq)$Answer:
$2FeSO_4(s) \overset{heat}{\rightarrow} Fe_2O_3 (s) +SO_2 (g) +SO_3 (g)$Question 28. Why do fire flies glow at night?
Answer:
Fire flies produces an enzyme called as luciferase which carries oxidation of Magnesium Because of oxidation of Magnesium in presence of atmospheric oxygen fire flies’ glows in the night. This phenomenon of glowing by living organisms is called bioluminescence.Answer:
Grapes on the plant do not ferment because of defense mechanism of plants. When grapes are plucked from plant, grapes reacts with yeast to carry out fermentation. Here sugar changes to alcohol and it is a chemical change.Question 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
Answer:
Physical changes only change the appearance of a substance, not its chemical composition.Here some short answer type questions from NCERT Exemplar Solutions for Class 10 Science Chapter 1 Chemical Reactions and Equation are given for practice. This section contains important questions that are asked in the exams.Practice short answer types from the questions below.
Question 31. During the reaction of some metals with dilute hydrochloric acid, 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
(d) Some bubbles of a gas are seen when lead (Pb) is reacted with the acid.
Explain these observations giving suitable reasons.
Answer:
a) There will not be any reaction between silver and dilute HCl as silver lies in low reactive series of metals.Answer:
Compound X is Calcium oxide.Question 33. Write a balanced chemical equation for each of the following reactions and also classify them.
(a) Lead acetate solution is treated with dilute hydrochloric acid to form lead chloride and acetic acid solution.
(b) A piece of sodium metal is added to absolute ethanol to form sodium ethoxide and hydrogen gas.
(c) Iron (III) oxide on heating with carbon monoxide gas reacts to form solid iron and liberates carbon dioxide gas.
(d) Hydrogen sulphide gas reacts with oxygen gas to form solid sulphur and liquid water.
Answer:
(a) $Pb(CH3COO)_2 + 2HCl \rightarrow PbCl_2 + CH_3COOH$Question 34. Why do we store silver chloride in dark coloured bottles?
Answer:
Silver chloride decomposes into silver and chlorine gas when exposed to sunlight.Question 35. Balance the following chemical equations and identify the type of chemical reaction.
(a) $Mg(s) + Cl_2(g) \rightarrow MgCl_2(s)$
(b) $HgO(s) \rightarrow Hg(l) + O_2(g)$
(c) $Na(s) + S(s) \rightarrow Na_2S(s)$
(d) $TiCl_4 (l) + Mg(s) \rightarrow Ti(s) + MgCl_2(s)$
(e) $CaO(s) + SiO_2(s) \rightarrow CaSiO_3(s)$
(f) $H_2O_2 (l) \rightarrow H_2O(l) + O_2(g)$
Answer:
(a)$Mg(s) + Cl_2(g) \rightarrow MgCl_2(s)$Question 36. A magnesium ribbon is burnt in oxygen to give a white compound X accompanied by emission of light. If the burning ribbon is now placed in an atmosphere of nitrogen, it continues to burn and forms a compound Y.
(a) Write the chemical formulae of X and Y.
(b) Write a balanced chemical equation, when X is dissolved in water.
Answer:
(a) $2Mg + O_2 \rightarrow 2MgO$Question 37. Zinc liberates hydrogen gas when reacted with dilute hydrochloric acid, whereas copper does not. Explain why?
Answer:
Zinc is more reactive than copper as Zinc is placed above Hydrogen and Copper is placed below hydrogen in the activity series of metals. Because of this Zinc reacts with HCl whereas Copper will not react.Question 38. A silver article generally turns black when kept in the open for a few days. The article when rubbed with toothpaste again starts shining.
(a) Why do silver articles turn black when kept in the open for a few days? Name the phenomenon involved.
(b) Name the black substance formed and give its chemical formula.
Answer:
a) Silver reacts with $H_2S$ present in the atmosphere to form a black color compound Silver Sulphide. This phenomenon is called as corrosion.Question 39. On heating blue coloured powder of copper (II) nitrate in a boiling tube, copper oxide (black), oxygen gas and a brown gas X is formed
(a) Write a balanced chemical equation of the reaction.
(b) Identity the brown gas X evolved.
(c) Identity the type of reaction.
(d) What could be the pH range of aqueous solution of the gas X?
Answer:
Blue coloured powder of copper (II) nitrate = $Cu(NO_3)_2$Question 40. Give the characteristic tests for the following gases
(a) $CO_2$
(b) $SO_2$
(c) $O_2$
(d) $H_2$
Answer:
(a) Pass $CO_2$ into limewater which will turn limewater milky. This is the confirmation test for the presence of carbon-dioxide.Question 41. What happens when a piece of
(a) zinc metal is added to copper sulphate solution?
(b) aluminium metal is added to dilute hydrochloric acid?
(c) silver metal is added to copper sulphate solution?
Also, write the balanced chemical equation if the reaction occurs
Answer:
(a) When Zinc is added to copper sulphate solution Zinc displaces copper to form Zinc sulphate.
$Zn(s)+ CuSO_4(aq) \rightarrow ZnSO_4 (aq) + Cu(s)$
(b) Aluminium metal reacts with dilute HCl to for Aluminum Chloride and Hydrogen gas is evolved in the reaction.
$2Al (s)+ 6HCl (aq) \rightarrow 2AlCl_3(aq) + 3H_2$
(c) When silver metal is added to Copper Sulphate solution there will not be any reaction as silver is non-reactive metal.
Question 42. What happens when zinc granules are treated with dilute solution of H2SO4, HCl, HNO3, NaCl and NaOH, also write the chemical equations if reaction occurs.
Answer:
When zinc granules are treated with dilute solution of the following:
(i) $\mathrm{H}_2 \mathrm{SO}_4$
When zinc granules are treated with dilute solution of sulphuric acid, zinc sulphate solution is formed along with hydrogen gas.
$\mathrm{Zn}(\mathrm{s}) \quad+\mathrm{H}_2 \mathrm{SO}_4(\mathrm{aq}) \quad \rightarrow \quad \mathrm{ZnSO}_4(\mathrm{aq})+\mathrm{H}_2(\mathrm{~g})$
(ii) HCl
When zinc granules are treated with dilute solution of hydrochloric acid, zinc chloride solution is obtained with the evolution of hydrogen gas.
$\mathrm{Zn}(\mathrm{s}) \quad+2 \mathrm{HCl}(\mathrm{aq}) \quad \rightarrow \quad \mathrm{ZnCl}_2(\mathrm{aq}) \quad+\mathrm{H}_2(\mathrm{~g})$
(iii) $\mathrm{HNO}_3$
When zinc granules are treated with dilute solution of nitric acid, an aqueous solution of zinc nitrate is formed along with water and nitrous oxide.
$4 \mathrm{Zn}(\mathrm{s}) \quad+10 \mathrm{HNO}_3(\mathrm{aq}) \quad \rightarrow 4 \mathrm{Zn}\left(\mathrm{NO}_3\right)_2(\mathrm{aq}) \quad+\mathrm{H}_2 \mathrm{O}(\mathrm{I}) \quad+\mathrm{N}_2 \mathrm{O}$
(iv) NaCl
Zinc granules on treatment with NaCl, do not undergoes any reaction as sodium is a reactive metal than zinc (sodium is placed above zinc in the reactivity series), and cannot displace sodium from its salt solution of sodium chloride.
$\mathrm{Zn}(\mathrm{s}) \quad+\mathrm{NaCl}(\mathrm{aq}) \quad \rightarrow \quad$ No Reaction
(v) NaOH:
Zinc metal reacts with alkali to form salt and evolve hydrogen gas.
$\mathrm{Zn}(\mathrm{s}) \quad+2 \mathrm{NaOH}(\mathrm{aq}) \quad \rightarrow \quad \mathrm{Na}_2 \mathrm{ZnO}_2(\mathrm{aq}) \quad+\mathrm{H}_2(\mathrm{~g})$
Get your results instantly with our calculator!
The following are the long-answer type questions that needs more practice. These NCERT Exemplar Class 10 Science Chapter 1 Chemical Reactions and Equation important questions are frequently asked in the exams. Long-answer type questions are covered to improve your subject knowledge and conceptual thinking:
Question 43. On adding a drop of barium chloride solution to an aqueous solution of sodium sulphite, white precipitate is obtained.
(a) Write a balanced chemical equation of the reaction involved
(b) What other name can be given to this precipitation reaction?
(c) On adding dilute hydrochloric acid to the reaction mixture, white precipitate disappears. Why?
Answer:
(a) On adding a drop of Barium Chloride solution to an aqueous solution of sodium sulphite, barium sulphite is obtained which is white color precipitate.Answer:
Dilute HClSome NCERT Exemplar Class 10 Science Chapter 1 Chemical Reactions and Equation questions and answers are given below that will help you tackle complex problems. The questions below will help you evaluate your understanding of the concepts.
Question 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) $\mathrm{KMnO}_4$ is an oxidising agent, it oxidises $\mathrm{FeSO}_4$
(b) $\mathrm{FeSO}_4$ acts as an oxidising agent and oxidises $\mathrm{KMnO}_4$
(c) The colour disappears due to dilution; no reaction is involved
(d) $\mathrm{KMnO}_4$ is an unstable compound and decomposes in the presence of $\mathrm{FeSO}_4$ to a colorless compound.
Answer:
The purple color of the solution was due to potassium permanganate, which acts as an oxidizing agent. When it oxidises $\mathrm{FeSO}_4$ the purple colour fades away
Hence, the correct option is option (a).
Question 2: A sample of a chromium-containing alloy weighing 3.45 g was dissolved in acid, and all the chromium in the sample was oxidized to $\mathrm{CrO}_4^{2-}$. It was then found that 3.0 g of $\mathrm{Na}_2 \mathrm{SO}_3$ was required to reduce the $\mathrm{CrO}_4^{2-}$ to $\mathrm{CrO}_2^{-}$in a basic solution, with $\mathrm{SO}_3^{2-}$ getting oxidized to $\mathrm{SO}_4^{2-}$. Then the \% of chromium in the alloy is $\qquad$ .
(Round off your answer to the nearest integer)
Answer:
The reaction involved is
$$
2 \mathrm{CrO}_4^{2-4}+3 \mathrm{SO}_3^{2-}+\mathrm{H}_2 \mathrm{O} \rightarrow 2 \mathrm{CrO}_2^{-}+3 \mathrm{SO}_4^{2-}+2 \mathrm{OH}^{-}
$$
Also,
$$
\begin{aligned}
\mathrm{molCrO}_4^{2-} & =\left(3.0 \mathrm{gNa}_2 \mathrm{SO}_3\right) \times\left(\frac{1 \mathrm{molNa}_2 \mathrm{SO}_3}{126 \mathrm{gNa}_2 \mathrm{SO}_3}\right) \times\left(\frac{1 \mathrm{molSO}_3^{2-}}{1 \mathrm{molNa}_2 \mathrm{SO}_3}\right) \times\left(\frac{2 \mathrm{molCrO}_4^{2-}}{3 \mathrm{molSO}_3^{2-}}\right) \\
& =1.58 \times 10^{-2} \mathrm{molCrO}_4^{2-}
\end{aligned}
$$
Since there is one mole of Cr in each mole of $\mathrm{CrO}_4^{2-}$, then the above number of moles $\mathrm{CrO}_4^{2-}$ is also equal to the number of moles of Cr that were present:
$0.0158 \mathrm{molCr} \times 52.00 \mathrm{~g} / \mathrm{mol}=0.825 \mathrm{gCr}$ in the original alloy.
$\%$ of $\mathrm{Cr}=(0.825 \mathrm{gCr} / 3.450 \mathrm{~g}$ sample $) \times 100 \%=23.9 \% \mathrm{Cr}$
Alternately,
gram equiv of $\mathrm{CrO}_4^{2-} \equiv$ gram equiv of $\mathrm{SO}_3^{2-}$
$\Rightarrow\left(\right.$ Moles of Cr or $\left.\mathrm{CrO}_4^{2-}\right) \times 3=\frac{3}{126 / 2}$
$\Rightarrow$ Moles of $\mathrm{Cr}=\frac{1}{63}$
Therefore, $\%$ of Cr in alloy $=\frac{52 / 63}{3.45} \times 100=23.92 \%$
Hence, the answer is (24).
Question 3: Which of the following methods can be used to prevent the food from getting rancid:
i. Storing the food in the air-tight containers
ii. Storing the food in refrigerator
iii. Keeping food in open
iv. Keeping food in moist atmosphere
(1) (i) and (ii)
(2) (i) and (iii)
(3) (iii) and (iv)
(4) All of the above
Answer:
Rancidity can be prevented by storing food in airtight containers because in airtight containers there is little exposure to oxygen then oxidation of fats and oils present in food is slowed down and thus rancidity is retarded. Rancidity can be prevented by keeping food in a refrigerator because in a refrigerator when the food is kept the oxidation of fats and oils in it is slowed down due to low temperature and thus rancidity is retarded.
Hence, the answer is the option (1).
Question 4: The white precipitates formed In a chemical reaction between sulphuric acid and barium chloride solution is of:
(1) Sulphur
(2) Barium sulphate
(3) Chlorine
(4) Silver chloride
Answer:
White precipitates formed In a chemical reaction between sulphuric acid and barium chloride solution is of Barium sulphate.
Hence, the answer is the option (2).
Question 5: Respiration is known as the process of combustion of glucose undergoes with oxygen in the cells of our body to produce energy, is a kind of:
(1) Exothermic process
(2) Reversible process
(3) Endothermic process
(4) Physical process
Answer:
Respiration, which is the process of combustion of glucose is an exothermic reaction.
Hence, the answer is the option (1).
To solve Class 10 Science NCERT Exemplar Solutions Chapter 1 Chemical Reactions and Equations questions, it is important to follow a systematic approach. It is recommended to strategies your study plan to solve the questions of this chapter. The following are the points that will help you build a good approach.
1. Recall the fundamental concepts like Chemical reaction, Balance the equation, types of chemical reaction, etc. Students can also follow Class 10 Science Chapter 1 Chemical Reactions and Equation notes to understand all these concepts better.
2. Learn about different kinds of reaction
3. Questions from balancing of chemical equations are asked frequently in exams to solve them effectively first convert the word equation into a chemical equation and balance it by ensuring equal atoms of each element on both sides.
4. To identify whether the change is Physical or Chemical, note down the indicators such as change in colour, evolution of gas, precipitate formation, or temperature change to identify reactions practically.
5. Practice again and again, as it will help in mastering NCERT Exemplar Class 10 Science Chapter 1 Chemical Reactions and Equation. Start with simpler problem,s then gradually move to difficult ones. Questions from this chapterare asked directly in the CBSE and State board exams.
Following are the important topics from the chapter Chemical Reactions and Equation. Practice more at Chemical Reactions and Equation Chapter 1 NCERT Exemplar Class 10 Science.
1.Chemical Equations
Writing Chemical Equation
Balanced Chemical Equations
2. Types of Chemical Reactions
Combination Reaction
Decomposition Reaction
Displacement Reaction
Double Displacement Reaction
Oxidation And Reduction
3. Have you observed the effects of oxidation in everyday life
Corrosion
Rancidity
NCERT Exemplar Solutions for Class 10 Science Chapter 1 Chemical Reactions and Equation helps students to understand the concepts of chemistry in Class 10. The advantages of using these solutions are given below:
These solutions offer well-structured answers to advanced conceptual and application-based questions, helping students strengthen understanding across all topics.
NCERT Solutions for Class 10 Science provide clear and accurate answers to all textbook questions. These chapter wise solutions help students understand concepts easily and prepare effectively for exams:
Students can refer to the links given below for the NCERT subject-wise solutions:
Students can refer to the links given below for the NCERT subject-wise notes:
Students can refer to the links given below for the NCERT Books and Syllabus of class 10:
Frequently Asked Questions (FAQs)
First, count the atoms of each element on both sides of a chemical equation. Adjust the coefficients to make the number of atoms equal on both sides. Start with the most complex molecule and balance one element at a time.
An exothermic reaction is a type of reaction in which heat is released, e.g., burning fuel and respiration. On the other hand, an endothermic reaction is one in which heat is absorbed that causes the surroundings to cool down. For example, photosynthesis and melting ice
Looking around the surroundings, you can find a bunch of examples. Some of them are given below:
1. Rusting of iron - When iron reacts with oxygen and water it forms rust.
2. Cooking food - Heat causes chemical changes in ingredients to form new substances.
3. Digestion - The food we eat breaks down into simpler substances in our body.
Respiration is considered an exothermic reaction because it releases energy in the form of heat. When glucose and oxygen combine during respiration, it produces carbon dioxide, water, and energy. The body uses this energy to stay warm and carry out several tasks.
A physical change is a reversible change in which no new substance is formed, while a chemical change is an irreversible change where one or more new substances are formed.
Chemical Reactions and Equation Chapter 1 NCERT Exemplar provide detailed, step-wise answers to advanced questions that help students understand reaction types, balancing equations, and application-based problems.
NCERT Exemplar solutions help you write chemical equations by giving clear, step-by-step examples of balancing and identifying reaction types, improving accuracy and understanding.
The main objective of the NCERT Exemplar Solutions for Class 10 Science Chapter 1 is to provide students with in-depth explanations and step-by-step solutions to the problems and questions related to chemical reactions and equations.
NCERT Exemplar Solutions are highly beneficial for understanding chemical reactions and equations. They offer additional practice and examples that help clarify complex concepts, making it easier for students to grasp the material and apply it effectively in exams.
Yes, students can easily find NCERT Exemplar Solutions for Class 10 Science Chapter 1 Chemical Reactions and Equation online. Many educational websites and platforms offer free access to these solutions, allowing students to download or view them as needed. This accessibility provides additional support for students looking to supplement their learning.
A block of mass 0.50 kg is moving with a speed of 2.00 ms-1 on a smooth surface. It strikes another mass of 1.00 kg and then they move together as a single body. The energy loss during the collision is
| Option 1)
|
Option 2)
|
| Option 3)
|
Option 4)
|
An athlete in the olympic games covers a distance of 100 m in 10 s. His kinetic energy can be estimated to be in the range
| Option 1)
|
Option 2)
|
| Option 3)
|
Option 4)
|
A particle is projected at 600 to the horizontal with a kinetic energy . The kinetic energy at the highest point
| Option 1)
|
Option 2)
|
| Option 3)
|
Option 4)
|
In the reaction,
| Option 1)
|
Option 2)
|
| Option 3)
|
Option 4)
|
How many moles of magnesium phosphate, will contain 0.25 mole of oxygen atoms?
| Option 1)
0.02 |
Option 2)
3.125 × 10-2 |
| Option 3)
1.25 × 10-2 |
Option 4)
2.5 × 10-2 |
Law Admissions 2026 Open | Avail Merit-Based Scholarships
BBA/MBA/PGDM Early Bird Applications Deadline 06th Nov'26. Apply now using coupon code CAREER250 and get ₹250 off the application fee
Ranked #36 amongst institutions in Management by NIRF | 100% Placement
Globally Recognized by AACSB (US) & AMBA (UK) | 18 LPA Avg. CTC for PGPM 2026
NEET PG All India & State College Predictor with Admission Process Guide
Top B-School: Ranked #9 in NIRF Management Rankings 2025.