NCERT Solutions for class 10:Chemical Reactions and Equations
NCERT Solutions for class 10 Science Chapter 1:- Chemical Reactions and Equations
The chapter “NCERT Solutions for Class 10: Chemical Reactions and Equations” introduces students to the fundamentals of chemical reactions. In this chapter, students will first explore the various types of chemical reactions, such as combination, decomposition, displacement, and double displacement reactions. Furthermore, they will examine how these reactions occur and their practical applications. Additionally, students will gain insight into the real-world significance of these reactions in everyday life. Understanding these reactions is crucial as they play an essential role in daily life, from cooking to industrial processes. NCERT Solutions for class 10:Chemical Reactions and Equations
CBSE Solutions for class 10:Chemical Reactions and Equations:-From this chapter students get 4 Marks for every year.Therefore, students must prepare thoroughly in order to secure good marks in their exam. Furthermore, consistent practice and a clear understanding of the concepts will greatly improve their performance. In addition, reviewing past exams and seeking help with difficult topics will provide further reinforcement. Moreover, staying organized and managing time effectively will also contribute to better results. As a result, students can approach the exam with confidence and achieve their desired marks.
NCERT Solutions for class 10:Chemical Reactions and Equations:
chapter mostly contains practice-based questions. In addition, these questions are designed to help reinforce the concepts learned. Furthermore, they provide students with an opportunity to apply their knowledge and test their understanding. As a result, students can gain confidence in their ability to solve similar problems in the future.. Thorough knowledge and good practice will help learners score full marks on the questions asked in this chapter.
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CBSE Class 10 Science Chapter 1 NCERT Solutions
The topics covered in NCERT Solutions for Class 10 Science Chapter 1, “Chemical Reactions and Equations,” are: NCERT Solutions for class 10:Chemical Reactions and Equations
** 1.1 CHEMICAL EQUATIONS
Ø 1.1.1 Writing a Chemical Equation
Ø 1.1.2 Balanced Chemical Equations
** 1.2 TYPES OF CHEMICAL REACTIONS
Ø 1.2.1 Combination Reaction
Ø 1.2.2 Decomposition Reaction
Ø 1.2.3 Displacement Reaction
Ø 1.2.4 Double Displacement Reaction
Ø 1.2.5 Oxidation and Reduction
** 1.3 HAVE YOU OBSERVED THE EFFECTS OF OXIDATION REACTIONS IN EVERYDAY LIFE?
Ø 1.3.1 Corrosion
Ø 1.3.2 Rancidity
QUESTIONS and ANSWERS:
Chemical Reactions and Equations
In-text questions set 1 Page number – 6
1.Why should you clean a magnesium ribbon before burning it in the air?
Solution:
Magnesium gets covered with a layer of magnesium oxide when kept in air for a long time. This layer hinders the burning of magnesium. Hence, it is to be cleaned before burning.
2. Write a balanced equation for the following chemical reactions.
i) Hydrogen + Chloride —-> Hydrogen chloride
ii) Barium chloride + Aluminium sulphate —-> Barium sulphate + Aluminium chloride
iii) Sodium + Water —-> Sodium hydroxide + Hydrogen
Solution:
i) H2 + Cl2 → 2HCl
ii) 3BaCl2 + Al2(SO4)3 →3BaSO4 + 2AlCl3
iii) 2Na + 2H2O → 2NaOH + H2
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 solution of Sodium chloride.
ii) Sodium hydroxide solution in water reacts with the hydrochloric acid solution to produce Sodium chloride solution and water.
Solution:
i) BaCl2 + Na2SO4 → BaSO4 + 2NaCl
ii) NaOH + HCl → NaCl + H2O
In-text questions set 2 Page number – 10
1.They use a solution of a substance, ‘X,’ for whitewashing.
(i) Name the substance ‘X’ and write its formula.
(ii) Write the reaction of the substance ‘X’ named in (i) above with water.
Solution:
i) They use quicklime, also known as calcium oxide (CaO), in whitewashing.
ii) CaO + H2O → Ca(OH)2
Solution: (i) The solution of calcium oxide (or quicklime) in water is used for whitewashing.Its formula is CaO.
2.Why do you collect double the amount of gas in one of the test tubes in Activity 1.7 compared to the other? Name this gas.
Solution:
In activity 1.7, you collect twice as much gas in one of the test tubes as in the other because, as a result of hydrolysis, water releases H2 and O2 gas. Therefore, this difference in the amounts of gas collected occurs. Furthermore, the process of hydrolysis continues to release gases in varying quantities, contributing to the observed variation. As a result, the final volume of gas in each test tube reflects the difference in the rate of gas production.
Here, after electrolysis, the process releases two molecules of hydrogen and one molecule of oxygen gas; hence, you would collect twice as much hydrogen as oxygen. Moreover, this ratio is consistent throughout the reaction, further reinforcing the principle of electrolysis. As a result, the amounts of hydrogen and oxygen collected are predictable based on their molecular proportions. Therefore, this process demonstrates the clear relationship between the two gases during electrolysis.
In-text questions set 3 Page number – 13
1. Why does the colour of copper sulphate solution change when an iron nail is dipped in it?
Solution:
When you dip an iron nail in copper sulfate solution, the iron displaces copper from the copper sulfate because iron is more reactive than copper. Consequently, the color of the copper sulfate solution changes. As a result, you observe a noticeable shift in the solution’s appearance, indicating the occurrence of a chemical reaction. Furthermore, this change in color also serves as visual evidence of the displacement reaction taking place. Therefore, the reaction not only alters the solution’s color but also demonstrates the reactivity differences between iron and copper.The reaction is
Fe + CuSO4 → FeSO4 + Cu
2. Give an example of a double displacement reaction other than the one given in Activity 1.10.
Solution:
Reaction Between silver nitrate (AgNO3) and Sodium chloride (NaCl) is an example of a double displacement reaction.During the reaction, negative and positive ions trade positions, leading to the formation of a white silver chloride precipitate. Consequently, this ion exchange causes the appearance of the precipitate. Moreover, the formation of the silver chloride precipitate serves as clear evidence of the reaction taking place. As a result, you can visually observe the chemical change through the precipitation process.. The chemical reaction is given below.
Ag+ + NO3– + Na+ + Cl– → AgCl + Na+ + NO3–
3. Identify the substances that are oxidised and that are reduced in the following equation.
i) 4Na(s) + O2(g) → 2Na2O(s)
ii) CuO(s) + H2(g) → Cu(s) + H2O(l)
Solution:
In the first equation, sodium (Na) undergoes oxidation upon reacting with oxygen (O₂). On the other hand, in the second equation, copper (Cu) undergoes reduction upon reacting with hydrogen (H₂). As a result, copper gains electrons during the reaction. Additionally, this process leads to a change in the oxidation state of copper, further highlighting the reduction process. Therefore, the reaction demonstrates how hydrogen acts as a reducing agent in this scenario.
In redox reactions, oxidation involves the loss of electrons, which leads to an increase in the oxidation state of an element. Conversely, reduction involves the gain of electrons, resulting in a decrease in the oxidation state. As a result, these processes are interconnected, with oxidation and reduction occurring simultaneously. Furthermore, the transfer of electrons during these reactions plays a crucial role in the overall chemical changes. Therefore, understanding both oxidation and reduction is essential to comprehending redox reactions.
NCERT Solutions for class 10:
Chemical Reactions and Equations:-E X E R C I S E S:
- Which of the statements about the reaction below are incorrect?
2PbO(s) + C(s) → 2Pb(s) + CO2 (g)
(a) Lead is getting reduced.
(b) Carbon dioxide is getting oxidised.
(c) Carbon is getting oxidised.
(d) Lead oxide is getting reduced.
(i) (a) and (b) (ii) (a) and (c) (iii) (a), (b) and (c) (iv) all
Solution:
(i) (a) and (b)
Explanation: (a) This occurs because the process removes oxygen, which leads to a reduction in the oxidation state of the element. (b) Furthermore, the reaction adds the removed oxygen from lead to the elemental carbon, resulting in the formation of carbon dioxide.Therefore, both processes contribute to the overall chemical change.
2. Fe2O3 + 2Al → Al2O3 + 2Fe The above reaction is an example of a
(a) combination reaction.
(b) double displacement reaction.
(c) decomposition reaction.
(d) displacement reaction.
Solution:
The answer is 4. Displacement reaction.
Explanation: The aluminum metal displaces the oxygen from ferrous oxide to form aluminum oxide. In this reaction, aluminum, being a more reactive metal than iron (Fe), replaces iron in the compound.Therefore, aluminum (Al) will displace iron from its oxide.
As a result, the more reactive aluminum replaces iron in the compound. This type of chemical reaction, known as a displacement reaction, occurs when one element displaces another from its compound. Consequently, displacement reactions are commonly observed when a more reactive element interacts with a less reactive one.
Here, less reactive metal is displaced by more reactive metal.Since one-time displacement is occurring, it is called a single displacement reaction. In addition, this type of reaction involves the replacement of one element by another in a compound. As a result, a more reactive element displaces a less reactive one. Therefore, single displacement reactions are often observed in cases where reactivity differences between elements play a key role.
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.
Solution:
- Hydrogen gas and Iron chloride are produced.
Explanation: The Chlorine from Hydrogen chloride is displaced by the Iron fillings to undergo the following reaction.
2HCl + Fe → FeCl2 + H2
4. What is a balanced chemical equation? Why should chemical equations be balanced?
Solution:
A balanced equation is the one in which number of different atoms on both the reactant and product sides are equal. Balancing chemical equations is necessary for the reaction should obey The Law of Conservation of mass. Balancing the chemical equation has no defined method and is purely a trial-and-error attempt.
5. Translate the following statements into chemical equations and then balance them.
(a) Hydrogen gas combines with nitrogen to form ammonia.
Solution:
(a) Unbalanced: H2 + N2 → NH3
Balanced: 3H2 + N2 → 2NH3
(b) Hydrogen sulphide gas burns in air to give water and sulpur dioxide.
(b) Unbalanced: H2S + O2 → H2O + SO2
Balanced: 2H2S + 3O2 → 2H2O + 2SO2
(c) Barium chloride reacts with aluminium sulphate to give aluminium chloride and a precipitate of barium sulphate.
(c) Unbalanced:
BaCl2 + Al2(SO4)3 → AlCl3 + BaSO4
Balanced: 3BaCl2 + Al2(SO4)3 → 2AlCl3 + 3BaSO4
(d) Potassium metal reacts with water to give potassium hydroxide and hydrogen gas.
(d) Unbalanced: K + H2O → KOH + H2
Balanced: 2K + 2H2O → 2KOH + H2
6. Balance the following chemical equations.
(a) HNO3 +Ca(OH)2 → Ca(NO3 ) 2 + H2O
(b) NaOH + H2SO4 → Na2SO4 + H2O
(c) NaCl + AgNO3 → AgCl + NaNO3
(d) BaCl2 + H2 SO4 → BaSO4 + HCl
7. Write the balanced chemical equations for the following reactions.
(a) Calcium hydroxide + Carbon dioxide → 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
8. Write the balanced chemical equation for the following and identify the type of reaction in each case.
(a) Potassium bromide(aq) + Barium iodide(aq) → Potassium iodide(aq) + Barium bromide(s)
(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)
9. What does one mean by exothermic and endothermic reactions? Give examples.
Solution:
An endothermic reaction occurs when the system absorbs energy from the surroundings in the form of heat (for example, photosynthesis, melting of ice, evaporation). Conversely, an exothermic reaction happens when the system releases energy into the surroundings (examples: explosions, concrete setting, nuclear fission and fusion).
10. Why do we consider respiration an exothermic reaction? Explain.
Solution:
For the survival of life, we require energy. We obtain this energy from the food we eat. Through the process of digestion, the body breaks down food molecules into simpler molecules like glucose.
These substances come in contact with the Oxygen present in our body cells to form Carbon dioxide and water along with a certain amount of energy (Respiration process). Since respiration releases energy in the form of heat (which maintains our body temperature), we consider it an exothermic reaction. The reaction taking place is:
C6H12O6 + 6O2 → 6CO2 + 6H2O + Energy
11. Why are decomposition reactions called the opposite of combination reactions? Write equations for these reactions
Solution:This essentially explains that the decomposition reaction is the opposite of the combination reaction.
In most cases, the decomposition reaction is endothermic since, in this type of reaction, heat is absorbed from the surroundings or induced heat is used to break the bonds of the larger molecule. Consequently, the reaction requires an input of energy to proceed.
A few examples of decomposition reactions are
ZnCO3 → ZnO + CO2
CaCO3 + Energy → CaO + CO2
2HgO → 2Hg + O2.
12. Write one equation each for decomposition reactions where energy is supplied in the form of heat, light or electricity.
Solution:
(a) Thermal decomposition reaction (Thermolysis)
Decomposition of potassium chlorate: When heated strongly, potassium chlorate decomposes into potassium chloride and oxygen. As a result, this reaction is used for the preparation of oxygen. Therefore, it serves as an important method for generating oxygen in various applications.This reaction is used for the preparation of oxygen.
2KClO3 + Heat → 2KCl + 3O2
(b) Electrolytic decomposition reaction (Electrolysis)
Decomposition of sodium chloride: On passing electricity through molten sodium chloride, it decomposes into sodium and chlorine.
(a) Thermal decomposition reaction (Thermolysis)
Decomposition of potassium chlorate: When heated strongly, potassium chlorate decomposes into potassium chloride and oxygen. Consequently, this reaction produces both potassium chloride and oxygen gas. This reaction is used for the preparation of oxygen.
2KClO3 + Heat → 2KCl + 3O2
(b) Electrolytic decomposition reaction (Electrolysis)
Decomposition of sodium chloride: On passing electricity through molten sodium chloride, it decomposes into sodium and chlorine.
(c) Photodecomposition reaction (Photolysis)
Decomposition of hydrogen peroxide: In the presence of light, hydrogen peroxide decomposes into water and oxygen.
(c) Photodecomposition reaction (Photolysis)
Decomposition of hydrogen peroxide: In the presence of light, hydrogen peroxide decomposes into water and oxygen.
13. What is the difference between displacement and double displacement reactions? Write equations for these reactions.
Solution:
A displacement reaction is one when a more reactive substance displaces a less reactive one from its salt solution, whereas a double displacement reaction is one where a mutual exchange of ions happens between two compounds.
In a displacement reaction, only a single displacement takes place, whereas in the double displacement reaction, as the name suggests, two displacement takes place between the molecules.
Example:
Displacement reaction
Mg + 2HCl → MgCl2 + H2
Double displacement reaction
2KBr + BaI2 → 2KI + BaB
14. In the refining of silver, the recovery of silver from silver nitrate solution involved displacement by copper metal. Write down the reaction involved.
Solution:
Cu(s) + 2AgNO3(aq) → Cu(NO3)2(aq) + 2Ag(s)
15. What do you mean by a precipitation reaction? Explain by giving examples.
Solution:
When you combine two solutions containing soluble salts, a double displacement reaction takes place in which the compounds exchange ions. When one of such compounds formed is in solid form (that is insoluble in aqua), then it settles down at the bottom of the container. You call this solid the precipitate, and you term the respective reaction as the precipitation reaction. A few examples of precipitation reactions are
CdSO4(aq) + K2S(aq) → CdS(s) + K2SO4(aq)
2NaOH(aq) + MgCl2(aq) → 2NaCl(aq) + Mg(OH)2(s)
16. Explain the following in terms of gain or loss of oxygen with two examples each.
(a) Oxidation
Solution: (a) In a chemical reaction, when you add oxygen to an element to form its respective oxide, the element undergoes oxidation. Example:
4Na(s) + O2(g) → 2Na2O(s)
H2S + O2 → H2O + SO2
Solution: (b) In a chemical reaction, when you remove oxygen from a compound, it is said to be reduced. Therefore, the compound undergoes reduction as it gains electrons.
Example:
CuO(s) + H2(g) → Cu(s) + H2O(l)
2HgO → 2Hg + O2
NCERT Solutions for class10:Chemical Reactions and Equations PDF
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.
Solution:
The shiny brown-coloured element is Copper metal (Cu)When you heat the metal in air, it reacts with atmospheric oxygen to form copper oxide. As a result, the black-colored compound formed is copper oxide.
2Cu(s) + O2(g) → 2CuO(s)
18. Why do we apply paint on iron articles?
Solution:
They paint iron articles to prevent them from rusting. When left unpainted, the metal surface comes in contact with atmospheric oxygen, and, in the presence of moisture, it forms iron(III) oxide. However, if painted, the surface is protected and does not come in contact with moisture and air, thereby preventing rusting.
19.They flush oil and fat-containing food items with nitrogen. Why?
Solution:
The main purpose of flushing nitrogen into food packets that contain oil and fat items is to prevent rancidity, which occurs when the oil or fat reacts with oxygen, thereby releasing an unpleasant smell and taste. Consequently, by removing oxygen, nitrogen helps preserve the quality and flavor of the food.
Therefore, by flushing nitrogen, you create an unreactive surrounding, which in turn prevents rancidity. As a result, this process helps maintain the freshness of the food.
20. Explain the following terms with one example each. (a) Corrosion (b) Rancidity
Solution:
(a) Corrosion is a process where a refined metal is oxidised by atmospheric oxygen to form a more stable compound, such as oxides. The metal gradually degrades during the corrosion process. Rusting of iron is a good example of corrosion, where the iron reacts to form iron oxide. People spend millions of dollars annually to prevent rusting on bridges and other monuments.
(b) The condition produced by the aerial oxidation of the oil and fat present in the food material that produces an unpleasant taste and smell. The rancidity is retarded when the food is kept inside the refrigerator since the low temperature does not promote the oxidation reaction.
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