NCERT Class 10 Science Chapter 1 Intext Question Answer: Chemical Reactions and Equations are an important part of the Class 10 Science curriculum that helps students understand the various types of chemical reactions. The Science Class 10 Chapter 1 PDF comprises in-text and exercise questions, which are of great essentiality from an exam point of view. Therefore, it is crucial that students know the answers in a well-formatted manner. This article is designed to guide the students through these questions and give them the right answers. To get the help, the chemical reactions and equations class 10 questions and answers PDF can be downloaded here for free.
NCERT Class 10 Chemical Reactions And Equations Solutions
Here, all the questions of NCERT Class 10 Chapter 1 Chemical Reactions and Equations are provided along with their answers. Students can check the solutions for intext as well as the exercise solutions.
NCERT Class 10 Science Chapter 1 Intext Question Answer Page Number 6
- Why should a magnesium ribbon be cleaned before burning in air?
Answer: Magnesium ribbon needs to be cleaned before burning in air because it forms a thin layer of magnesium oxide (MgO) on its surface when exposed to air. This oxide layer hinders the burning process.
The presence of the oxide layer makes it harder for oxygen in the air to react with the underlying magnesium, hindering the complete and efficient burning of the ribbon.
The oxide layer acts like a physical barrier, further slowing down the reaction between oxygen and magnesium.
Therefore, cleaning the magnesium ribbon removes this oxide layer, exposing fresh magnesium metal for a faster, more vigorous reaction with oxygen, resulting in the characteristic bright white flame.
- Write the balanced equation for the following chemical reactions.
(i) Hydrogen + Chlorine → Hydrogen chloride
(ii) Barium chloride + Aluminium sulphate → Barium sulphate + Aluminium chloride
(iii) Sodium + Water → Sodium hydroxide + Hydrogen
Answer:
(i) Hydrogen + Chlorine → Hydrogen chloride
- H2(g) + Cl2(g) → 2HCl(g)
(ii) Barium chloride + Aluminium sulphate → Barium sulphate + Aluminium chloride
- 3BaCl2(s) + Al2(SO4)3(s) → 3BaSO4 (s) + 2AlCl3 (s)
(iii) Sodium + Water → Sodium hydroxide + Hydrogen
- 2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g)
- 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 the solution of sodium chloride.
(ii) Sodium hydroxide solution (in water) reacts with hydrochloric acid solution (in water) to produce sodium chloride solution and water.
Answer:
(i) Solutions of barium chloride and sodium sulphate in water react to give insoluble barium sulphate and the solution of sodium chloride.
- 3BaCl2(aq) + Na2SO4(aq) → BaSO4(s) + 2NaCl(aq)
(ii) Sodium hydroxide solution (in water) reacts with hydrochloric acid solution (in water) to produce sodium chloride solution and water.
- NaOH(aq) + HCl(aq) → NaCl(aq) + H2O(l)
In these equations:
- (aq)indicates that the substance is in an aqueous solution.
- (s) indicates that the substance is a solid.
- (l) indicates that the substance is in the liquid state.
NCERT Class 10 Science Chapter 1 Intext Question Answer Page Number 10
- A solution of a substance ‘X’ is used 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.
Answer: (i) Name the substance ‘X’ and write its formula:
- The substance ‘X’ used for whitewashing is calcium oxide, commonly known as
- Formula: CaO
(ii) Write the reaction of the substance ‘X’ named in (i) above with water:
The reaction of calcium oxide (CaO) with water produces calcium hydroxide, which is used for whitewashing.
CaO(s) + H2O(l) →Ca(OH)2(aq)
In this reaction Calcium oxide (CaO) reacts with water (H₂O) to form calcium hydroxide [Ca(OH)₂], which is an aqueous solution used for whitewashing.
- Why is the amount of gas collected in one of the test tubes in Activity 1.7 double of the amount collected in the other? Name this gas.
Answer:
In the process of water electrolysis, water (H₂O) is decomposed into its constituent gases, hydrogen (H₂) and oxygen (O₂), using an electric current. The balanced chemical equation for this reaction is:
2H2O(l)→2H2(g)+O2(g)
Since the volume of a gas is proportional to the number of molecules, and because there are twice as many hydrogen molecules produced as oxygen molecules, the volume of hydrogen gas collected will be twice the volume of oxygen gas.
Hydrogen (H₂) is the gas that is collected in double the amount compared to oxygen (O₂) during the electrolysis of water.
NCERT Class 10 Science Chapter 1 Intext Question Answer Page Number 13
- Why does the colour of copper sulphate solution change when an iron nail is dipped in it?
Answer: The colour of copper sulphate (CuSO₄) solution changes when an iron nail is dipped in it due to a chemical reaction between iron and copper sulphate. Iron (Fe) displaces copper (Cu) from the copper sulphate solution because iron is more reactive than copper. The reaction forms iron(II) sulphate (FeSO₄) and copper metal. Iron(II) sulphate is pale green, which causes the blue colour of the copper sulphate solution to fade, and copper metal deposits as a reddish-brown layer on the nail. The chemical equation for this reaction is:
Fe(s) + CuSO4(aq) (blue) → FeSO4 (aq) (green) + Cu(s)
- Give an example of a double displacement reaction other than the one given in Activity 1.10.
Answer: When aqueous solutions of silver nitrate (AgNO₃) and sodium chloride (NaCl) are mixed, they react to form silver chloride (AgCl), which is an insoluble white precipitate, and sodium nitrate (NaNO₃), which remains in solution.
AgNO3(aq)+NaCl(aq)→AgCl(s)+NaNO3(aq)
Silver nitrate and sodium chloride exchange their ions to form silver chloride and sodium nitrate.
In the reaction between silver nitrate (AgNO₃) and sodium chloride (NaCl), the ions that are displaced are:
- Silver ion (Ag⁺)from silver nitrate.
- Sodium ion (Na⁺)from sodium chloride.
- Nitrate ion (NO₃⁻)from silver nitrate.
- Chloride ion (Cl⁻)from sodium chloride.
- Identify the substances that are oxidised and the substances that are reduced in the following reactions.
(i) 4Na(s) + O2(g) → 2Na2O(s)
(ii) CuO(s) + H2 (g) → Cu(s) + H2O(l)
Answer: In a chemical reaction, oxidation refers to the loss of electrons, while reduction refers to the gain of electrons. Let's analyze the given reactions:
(i) 4Na(s) + O₂(g) → 2Na₂O(s)
- Oxidised: Sodium (Na) because it loses electrons (0 to +1).
- Reduced: Oxygen (O₂) because it gains electrons (0 to -2).
(ii) CuO(s) + H₂(g) → Cu(s) + H₂O(l)
- Oxidised: Hydrogen (H₂) because it loses electrons (0 to +1).
- Reduced: Copper (Cu) because it gains electrons (+2 to 0).
NCERT Class 10 Science Chapter 1 Exercise Questions
- 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
Answer: Correct Option: (i) (a) and (b)
Lead oxide PbO(s) contains Pb2+ ions. In the reaction, PbO(s) is losing oxygen (reduction) and forming Pb(s). Therefore, lead oxide is indeed being reduced, not lead.
Carbon in C(s) is going from an oxidation state of 0 to +4 in CO2(g). This means not carbon dioxide but carbon is losing electrons and thus being oxidized.
Also Read:
- 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.
Answer: (d) displacement reaction.
- 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.
Answer: When dilute hydrochloric acid (HCl) is added to iron fillings (Fe), the following reaction occurs:
Fe+2HCl→FeCl2+H2
Here's what happens:
- Iron (Fe) reacts with hydrochloric acid (HCl) to produce iron chloride (FeCl2) and hydrogen gas (H2).
Thus, correct option is (a) Hydrogen gas and iron chloride are produced.
- What is a balanced chemical equation? Why should chemical equations be balanced?
Answer: A balanced chemical equation is a representation of a chemical reaction that follows the law of conservation of mass, which states that matter cannot be created or destroyed in a chemical reaction. In other words, the number of atoms of each element must be the same on both sides of the equation.
Chemical equations must be balanced because of the law of conservation of mass, which states that matter cannot be created or destroyed in a chemical reaction. This means:
- The total number of atoms of each element must be the same on both sides of the equation.
- If an equation is not balanced, it suggests that atoms have either been created or destroyed, which violates this fundamental law of nature.
- Translate the following statements into chemical equations and then balance them.
(a) Hydrogen gas combines with nitrogen to form ammonia.
(b) Hydrogen sulphide gas burns in air to give water and sulpur dioxide.
(c) Barium chloride reacts with aluminium sulphate to give aluminium chloride and a precipitate of barium sulphate.
(d) Potassium metal reacts with water to give potassium hydroxide and hydrogen gas.
Answer: (a) 3H2+N2→2NH3
(b) 2H2S+3O2→2H2O+2SO2
(c) 3BaCl2+Al2(SO4)3→2AlCl3+3BaSO4
(d) 2K+2H2O→2KOH+H2
- 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 + H2SO4 → BaSO4 + HCl
Answer: (a) 2HNO3 +Ca(OH)2 → Ca(NO3)2 + 2H2O
(b) 2NaOH + H2SO4 → Na2SO4 + 2H2O
(c) NaCl + AgNO3 → AgCl + NaNO3
(d) BaCl2 + H2SO4 → BaSO4 + 2HCl
- 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
Answer: (a) Ca(OH)2+CO2→CaCO3+H2O
(b) Zn+2AgNO3→Zn(NO3)2+2Ag
(c) 2Al+3CuCl2→2AlCl3+3Cu
(d) BaCl2+K2SO4→BaSO4+2KCl
Also Read:
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- Avogadro’s Number: Definition, Value, Meaning, Unit and Symbol
- Magnetic Field: Formula, Properties, and Applications
- Archimedes' Principle: Formula, Derivation, Applications and Examples
- 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)
Answer: (a) 2KBr(aq)+BaI2(aq)→2KI(aq)+BaBr2 (Double displacement (precipitation) reaction)
(b) ZnCO3(s)→ZnO(s)+CO2(g) (Decomposition reaction)
(c) H2(g)+Cl2(g)→2HCl(g) (Combination reaction)
(d) Mg(s)+2HCl(aq)→MgCl2(aq)+H2(g) (Single displacement reaction)
- What does one mean by exothermic and endothermic reactions? Give examples.
Answer: Exothermic Reactions: An exothermic reaction is a chemical reaction that releases energy in the form of heat or light. During this type of reaction, the energy of the products is lower than the energy of the reactants, and the excess energy is released to the surroundings. As a result, the surroundings become warmer.
Examples of exothermic reactions:
- Combustion of methane:CH4+2O2→CO2+2H2O+heat
- Respiration:C6H12O6+6O2→6CO2+6H2O+energy
- Reaction of sodium with water:2Na+2H2O→2NaOH+H2+heat
Endothermic Reactions: An endothermic reaction is a chemical reaction that absorbs energy from its surroundings in the form of heat. During this type of reaction, the energy of the products is higher than the energy of the reactants, and energy is taken in from the surroundings. As a result, the surroundings become cooler.
Examples of endothermic reactions:
- Photosynthesis:6CO2+6H2O+sunlight→C6H12O6+6O2
- Decomposition of calcium carbonate:CaCO3→CaO+CO2(heat absorbed)
- Dissolving ammonium nitrate in water:NH4NO3+H2O→NH4OH+HNO3(heat absorbed)
- Why is respiration considered an exothermic reaction? Explain.
Answer: Respiration is considered an exothermic reaction because it releases energy. During respiration, glucose (C6H12O6) reacts with oxygen (O2) to produce carbon dioxide (CO2), water (H2O), and energy. The chemical equation for respiration is:
C6H12O6+6O2→6CO2+6H2O+energy
This reaction releases energy because the total energy of the products (carbon dioxide and water) is lower than the total energy of the reactants (glucose and oxygen). The excess energy is released in the form of heat, which is used by the body to perform various functions and maintain body temperature. This release of energy makes respiration an exothermic reaction.
- Why are decomposition reactions called the opposite of combination reactions? Write equations for these reactions.
Answer: Decomposition reactions and combination reactions are considered opposites because they involve reverse processes in terms of the formation and breaking down of compounds.
In a combination reaction, two or more reactants combine to form a single product. This process involves the synthesis of a new compound from simpler substances.
In a decomposition reaction, a single compound breaks down into two or more simpler products. This process involves the breakdown of a compound into its component elements or simpler compounds.
- Write one equation each for decomposition reactions where energy is supplied in the form of heat, light or electricity.
Answer:
- Heat (Thermal Decomposition): CaCO3→heat→CaO+CO2
- When calcium carbonate (limestone) is heated, it decomposes into calcium oxide (lime) and carbon dioxide gas.
- Light (Photodecomposition): 2AgCl→light→2Ag+Cl2
- When silver chloride is exposed to light, it decomposes into silver metal and chlorine gas.
- Electricity (Electrolytic Decomposition): 2H2O→electricity→2H2+O2
- When water undergoes electrolysis, it decomposes into hydrogen gas and oxygen gas.
- What is the difference between displacement and double displacement reactions? Write equations for these reactions.
Answer:
| Feature | Displacement Reaction | Double Displacement Reaction |
| Definition | A reaction where one element replaces another element in a compound. | A reaction where the ions of two compounds exchange places to form two new compounds. |
| General Form | A + BC → AC + B | AB + CD → AD + CB |
| Example | Zn+CuSO4→ZnSO4+Cu | Na2SO4+BaCl2→BaSO4+2NaCl |
- In the refining of silver, the recovery of silver from silver nitrate solution involved displacement by copper metal. Write down the reaction involved.
Answer: In the refining of silver, silver can be recovered from a silver nitrate solution by displacement using copper metal. The reaction involved is a single displacement reaction where copper displaces silver from silver nitrate. The chemical equation for this reaction is:
Cu+2AgNO3→2Ag+Cu(NO3)2
- What do you mean by a precipitation reaction? Explain by giving examples.
Answer: A precipitation reaction is a type of chemical reaction in which two soluble salts in aqueous solutions react to form an insoluble solid, called a precipitate, and another soluble compound. The insoluble solid formed is known as the precipitate, and it usually settles out of the solution or forms a suspension.
Example 1: Reaction between Sodium Chloride and Silver Nitrate When aqueous solutions of sodium chloride (NaCl) and silver nitrate (AgNO3) are mixed, they react to form an insoluble precipitate of silver chloride (AgCl) and a soluble compound, sodium nitrate (NaNO3).
NaCl(aq)+AgNO3(aq)→AgCl(s)+NaNO3(aq)
In this reaction, silver chloride (AgCl) is the white precipitate formed.
Example 2: Reaction between Barium Chloride and Sulfuric Acid When aqueous solutions of barium chloride (BaCl2) and sulfuric acid (H2SO4) are mixed, they react to form an insoluble precipitate of barium sulfate (BaSO4) and hydrochloric acid (HCl).
BaCl2(aq)+H2SO4(aq)→BaSO4(s)+2HCl(aq)
In this reaction, barium sulfate (BaSO4) is the white precipitate formed.
- Explain the following in terms of gain or loss of oxygen with two examples each.
(a) Oxidation
(b) Reduction
Answer: (a) Oxidation refers to the gain of oxygen by a substance or the loss of electrons from a substance during a chemical reaction.
For example; 2Mg+O2→2MgO
In this reaction, magnesium (Mg) gains oxygen to form magnesium oxide (MgO).
(b) Reduction refers to the loss of oxygen by a substance or the gain of electrons by a substance during a chemical reaction.
For example; CuO+H2→Cu+H2O
In this reaction, copper(II) oxide (CuO) loses oxygen to form copper (Cu).
- A shiny brown coloured element ‘X’ on heating in air becomes black in colour. Name the element ‘X’ and the black coloured compound formed.
Answer: The shiny brown colored element 'X' is copper (Cu). When copper is heated in air, it reacts with oxygen to form a black-colored compound called copper(II) oxide (CuO).
The reaction can be represented by the following chemical equation:
2Cu+O2→2CuO2
- Why do we apply paint on iron articles?
Answer: We apply paint on iron articles to prevent corrosion. Corrosion, specifically rusting, occurs when iron reacts with oxygen and moisture in the environment, forming iron oxide (Fe₂O₃). This reaction can be represented as:
4Fe+3O2+6H2O→4Fe(OH)3
Painting creates a protective barrier that blocks oxygen and moisture from reaching the iron surface, thereby inhibiting the electrochemical reaction that leads to rust formation. This helps in prolonging the lifespan and maintaining the structural integrity of iron articles.
- Oil and fat-containing food items are flushed with nitrogen. Why?
Answer: Oil and fat-containing food items are flushed with nitrogen to prevent oxidation. Oxidation occurs when these foods react with oxygen in the air, leading to rancidity, which spoils the food and creates off-flavours and odours. Flushing with nitrogen, an inert gas, displaces the oxygen, thus preserving the quality, flavour, and shelf life of the food by preventing oxidative reactions.
- Explain the following terms with one example each.
(a) Corrosion
(b) Rancidity
Answer: (a) Corrosion: It is the gradual destruction or deterioration of metals due to chemical reactions with their environment, often involving oxygen and moisture.
Rusting of iron is a common example of corrosion. When iron is exposed to air and moisture, it reacts to form iron oxide (rust), which weakens the metal over time.
4Fe+3O2+6H2O→4Fe(OH)3
(b) Rancidity
Definition: Rancidity is the spoilage of fats and oils in food, resulting in an unpleasant taste and odour, caused by oxidation or hydrolysis.
Example: When butter is left out at room temperature for too long, it can become rancid. This happens as the fats in the butter react with oxygen in the air, producing off-flavours and a foul smell.
Unsaturated fat+O2→Hydroperoxide (rancid compound))
To download these solutions in PDF format, click on the link below:
| Download NCERT Class 10 Science Chapter 1 Chemical Reactions and Equations Solution Manual PDF |
These solutions follows the latest CBSE Class 10 Science syllabus 2024-25 and the updates NCERT textbook thus, do not include the deleted topics.
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