Class 10th chemistry is a part of the class 10 science curriculum. Class 10 chemistry syllabus includes, chemical reactions and equations, acid, bases and salt, metals and non-metals, carbon and its compounds and periodic table. Class 10th chemistry is an important part of the class 10 science syllabus. This Class 10 Chemistry page contains all the topics that fall under each chapter of the class 10 chemistry syllabus as per the NCERT textbook. Students may follow the links on the subtopics to access free study material on the associated concepts (prepared by chemistry subject experts for CBSE students). Furthermore, an overview of all the chapters and topics in the CBSE class 10 chemistry textbooks can also prove useful while crafting a preparation strategy for the CBSE board examination and other competitive examinations. Chemical reactions and equations class 10 is the first chapter. Let us take a look. At the end of this page, you will find, chemical reaction and equation class 10 MCQ questions for you to solve.

Chemical Reactions and Equations  Class 10

• Chemical reactions

What is a Chemical Reaction? 

A chemical reaction is in which the bonds are broken within reactant molecules, and new bonds are formed within product molecules in order to form a new substance. Chemical reactions are all around us, from the metabolism of food in our body to how the light we get from the sun is the result of chemical reactions. Before beginning with chemical reactions, it is important to know about physical and chemical changes.

A burning candle is the best example of physical and chemical change. Take a candle and light it. As time passes, we can observe that the candle changes to wax. If you cover the candle with a jar, it will extinguish.

In the demonstration, burning of the candle is a chemical change while conversion of the candle to wax is a physical change. In a physical change, there is basically a change of state of the substance but in the case of a chemical change mostly a new substance is formed in which either energy is given off or absorbed. Thus, we can conclude that chemical changes are accompanied by certain physical changes.

Basic Concepts of Chemical Reactions

A Chemical Reaction is a process that occurs when two or more molecules interact to form a new product(s).

Compounds that interact to produce new compounds are called reactants whereas the newly formed compounds are called products.

Chemical reactions play an integral role in different industries, customs, and even in our daily life. They are continuously happening in our general surroundings; for example, rusting of iron, pottery, fermentation of wine and so on.

In a chemical reaction, a chemical change must occur which is generally observed with physical changes like precipitation, heat production, colour change etc.

A reaction can take place between two atoms or ions or molecules, and they form a new bond and no atom is destroyed or created but a new product is formed from reactants.

The rate of reaction depends on and is affected by factors like pressure, temperature, and the concentration of reactants.

Chemical Equations

Due to the vast amounts of chemical reactions happening around us, a nomenclature was developed to simplify how we express a chemical reaction in the form of a chemical equation. A chemical equation is nothing but a mathematical statement that symbolizes the product formation from reactants while stating certain conditions for which the reaction has been conducted.

• Balanced chemical equation

A balanced chemical equation has equal numbers of atoms for each element involved in the reaction and are represented on the reactant and product sides. This is a requirement the equation must satisfy to be consistent with the law of conservation of matter. It may be confirmed by simply summing the numbers of atoms on either side of the arrow and comparing these sums to ensure they are equal. 

Balanced chemical equation example:

The equation for the reaction between methane and oxygen to yield carbon dioxide and water below is a balanced reaction:

CH4+2O2→CO2+2H2O

• Types of chemical reactions

The basis for different types of reactions is the product formed, the changes that occur, the reactants involved and so on. Different types of reactions are

• Combustion reaction
• Decomposition reaction
• Neutralization reaction
• Redox Reaction
• Precipitation or Double-Displacement Reaction
• Synthesis reaction

1. 
   Combustion Reaction

A combustion reaction is a reaction with a combustible material with an oxidizer to give an oxidized product. An oxidizer is a chemical a fuel requires to burn, generally oxygen.

2. Decomposition Reaction

A Decomposition reaction is a reaction in which a single component breaks down into multiple products. Certain changes in energy in the environment have to be made like heat, light or electricity breaking bonds of the compound. 

3. Neutralization Reaction

A Neutralization reaction is basically the reaction between an acid and a base giving salt and water as the products. The water molecule formed is by the combination of OH– ions and H+ ions. The overall pH of the products when a strong acid and a strong base undergo a neutralization reaction will be 7.

4. Redox Reaction

A REDuction-OXidation reaction is a reaction in which there is a transfer of electrons between chemical species.

5. Precipitation or Double-Displacement Reaction

It is a type of displacement reaction in which two compounds react and consequently, their anions and cations switch places forming two new products. 

6. Synthesis Reaction

A Synthesis reaction is one of the most basic types of reaction wherein multiple simple compounds combine under certain physical conditions giving out a complex product. The product will always be a compound.

• Oxidation and reduction

A reaction in which one reactant undergoes oxidation whereas the other gets reduced during the course of reaction are termed as oxidation-reduction reactions or redox reactions. Oxidation refers to the loss of electrons or increase in oxidation state by a molecule, atom, or ion. Reduction refers to the gain of electrons or decrease in oxidation state by a molecule, atom, or ion.

To understand these concepts better, don’t forget to solve chemical reaction and equation class 10 mcq questions. This chemical reaction and equation class 10 MCQ questions can be found in the practice section.  

Examples

Question 1

Why is the amount of gas collected in one of the test tubes in text book Activity 1.7 (i.e., electrolysis of water) double of the amount collected in the other? Name this gas. [CBSE 2015 (Delhi)]

Answer:

In Activity 1.7, water is electrolysed to give H2 gas at one electrode and O2 gas at the other electrode.

2H2O(l) → 2H2(g) + O2(g)

Thus two molecules of water on electrolysis give two molecules of hydrogen gas and one molecule of oxygen gas or in other words the amount of hydrogen gas collected would be double than that of oxygen gas.

Question 2

Why does the colour of copper sulphate solution change when an iron nail is dipped in it ?

OR

An iron nail is dipped in the solution of copper sulphate for about 30 minutes. State the change in colour observed. Give reason for the change. [CBSE 2015 (Delhi)]

Answer:

When an iron nail is dipped in copper sulphate solution, the displacement reaction takes place. The colour of the copper sulphate solution fades due to the formation of a light green solution of iron sulphate.

Question 3

Identify the substances that are oxidised and the substances which are reduced in the following reactions.

(i) 4Na(s) + O2(g) → 2Na2O(s)

(ii) CuO (s) + H2(g) → Cu (s) + H2O(l)

Answer:

(i) Substances oxidised is Na as it gains oxygen and oxygen is reduced.

(ii) Substances reduced is Cu as hydrogen is oxidised as it gains oxygen.

Question 4

Which of the statements about the reaction below are incorrect ?

2 PbO(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:

(i) (a) and (b)

Question 5

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.

Question 6

What happens when dilute hydrochloric acid is added to iron filings ? 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:

(a) Hydrogen gas and iron chloride are produced.

Question 7

What is a balanced chemical equation ? Why should chemical equations be balanced ?

Answer:

A balanced chemical equation has an equal number of atoms of different elements in the reactants and products.

The chemical equations should be balanced to satisfy the law of conservation of mass.

Question 8

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 sulphur 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 (g) + N2 (g) → 2NH3 (g)

(b) H2S (g) + 3O2 (g) → SO2 (g) + 2H2O(l)

(c) 3BaCl2 (aq) + Al2(SO4)3 (aq) → 2AlCl3 (aq) + 3BaSO4 ↓(s)

(d) 2K (s) + 2H2O (l) → 2KOH (aq) + H2 (g)

Question 9

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

Question 10

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 + 2 Ag

(c) 2Al + 3 CuCl2 → 2AlCl3 + 3 Cu

(d) BaCl2 + K2SO4 → BaSO4 + 2KCl

Question 11

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

(b) Zinc carbonate(s) → Zinc oxide (s) + Carbon dioxide (g) bromide(s)

(c) Hydrogen (g) + Chloride (g) → Hydrogen chloride (g)

(d) Magnesium (s) + Hydrochloric acid (aq) → Magnesium chloride (aq) + Hydrogen (g)

Answer:

(a) 2KBr (aq) + Bal2(aq) → 2Kl(aq) + BaBr2(s)

Type : Double displacement reaction

(b) ZnCO3 (s) → ZnO (s) + CO2 (g)

Type : Decomposition reaction

(c) H2 (g) + Cl2 (g) → 2HCl(g)

Type : Combination reaction

(d) Mg (s) + 2HCl (aq) → MgCl2 (aq) + H2 (g)

Type : Displacement reaction

Question 12

What does one mean by exothermic and endothermic reactions ? Give examples.

Answer:

Exothermic reactions : Those reactions in which heat is evolved are known as exothermic reactions. An exothermic reaction is indicated by writing “+ Heat”on the products side of an equation.

Example :

(i) C (s) + O2 (g) → CO2 (g) + Heat

(ii) N2 (g) + 3H2 (g) → 2NH3 (g) + Heat

Endothermic reactions : Those reactions in which heat is absorbed are known as endothermic reactions. An endothermic reaction is usually indicated by writing “Heat” on the product side of a chemical equation.

Examples :

(i) C (s) + 2S (s) → CS2 (l) – Heat

(ii) N2 (g) + O2 (g) → 2NO(g) – Heat

Question 13

Why is respiration considered an exothermic reaction? Explain.

Answer:

Respiration is an exothermic process because during respiration glucose combines with oxygen in the cells of our body to form carbon dioxide and water along with the production of energy.