Chemical Reactions and Equations is chapter 1 of class 10 Science of RBSE and one of the most important chapters for board exams.
Here you will find quick revision notes in easy language for fast learning and last-minute revision. After reading these notes, you can also go through the Questions of Chemical Reactions and Equations and practice MCQs for better understanding.
What is a Chemical Reaction?
A chemical reaction is a process in which one or more substance (reactants) change into new substances(product) with different properties.
Example
Mg + O2 →MgO
How to Identify a Chemical Reaction?
A chemical reaction has occurred if you observe;
i. Change in colour
ii. Change in temperature
iii. Formation of gas
iv. Formation of precipitate
v. Change in state
What is Chemical Equation?
A chemical equation is a symbolic representation of a chemical reaction using chemical formulas and
symbols. It shows the reactants, products, and the direction of the reaction.
Types of Chemical Equation
i. Word equation
Names of reactants and products are written.
Magnesium + oxygen →Magnesium oxide
ii. Skeletal equation or unbalanced equation
Formula and symbols of reactants and products are written.
Mg + O2 →MgO
iii. Balanced equation
Equal numbers of atoms of reactants and products on both sides according to the Law of conservation of mass.
2Mg + O2 →2MgO
Physical states and special conditions should be written
Solid – (s)
Liquid – (l)
Gaseous – (g)
Aqueous (aq)
Precipitate –(↓)
Evolution of gas- (↑)
Example : 3Fe(s) + 4H2O(g) →Fe2O4(s) + 4H2(g)
Types of Chemical Reactions
1. Combination Reaction
Two or more substances combine to form a one product.
A+B AB
CaO + H2O → Ca(OH)2 + heat
2. Decomposition Reaction
One compound break into two or more simpler substances.
AB → A +B
CaCO3 →CaO + CO2 (Thermal decomposition)
2H2O →2H2 + O2 (Electrolysis)
2AgCl →2Ag + Cl2
(Photochemical decomposition)
3. Displacement Reaction
A more reactive metal displaces a less reactive metal.
A + BC →AC + B
Zn + CuSO4 → FeSO4 + Cu
4. Double displacement reaction
Exchange of ions between two compounds.
Ab + CD →AD+ CB
Na2SO4 + BaCl2 →BaSO4↓ + 2NaCl
5. Precipitation Reaction
Formation of an insoluble solid during the
chemical reaction.
Pb(NO3)2 + 2KI →PbI2 ↓ + 2KNO3
6. Exothermic Reaction
Heat is released during chemical reaction.
CH4 +2O2 →CO2 +2H2O + heat
7. Endothermic Reaction
Heat is absorbed in the chemical reaction.
8. Oxidation Reaction
Addition of oxygen or removal of hydrogen.
2Mg + O2 →2MgO
9. Reduction Reaction
Removal of oxygen or addition of hydrogen
10. Redox Reaction
Oxidation and reduction reactions occur simultaneously; the reaction is called redox reaction.
CuO + H2 →Cu +H2O
Copper oxide is reduced to copper metal and hydrogen is oxidized to water.
Corrosion
Slow destruction of metals due to air and moisture
Example:- Rusting of iron
4Fe+ O2 + xH2O →2Fe2O3.xH2O(Rust)
Rancidity
Spoiling of food items containing fat and oil due to oxidation and has foul smell and taste.
Prevention
i. Airtight containers
ii. Refrigeration
iii. Adding antioxidants
iv. Nitrogen flushing in packets
Very important Reactions for Board Exams
1. Mg + O2 2MgO
2. Zn + H2SO4 ZnSO4 + H2
3. Na2SO4 + BaCl2 →BaSO4↓ + 2NaCl
4. 4Fe+ O2 + xH2O →2Fe2O3.xH2O(Rust)
5. Zn + CuSO4 → FeSO4 + Cu
Key Points to remember
i. Always balance chemical equations
ii. Mention physical states
iii. Identify the type of reaction
iv. Oxidation and reduction occur together.
v. Corrosion and rancidity are oxidation reactions.
Conclusion
These quick revision notes on Chemical Reactions and Equations Class 10 are useful for Board Exam revision, competitive exams, concept clarity and last minute preparation.
Short Questions with Answers – Chemical Reactions and Equations
Q1. What is a chemical reaction?
Answer – A chemical reaction is a process in which one or more substance changes into new substances with new properties.
Q2. What are reactants and products?
Answer – Reactants – Substances that take part in a chemical reaction.
Products- New substance formed after the reaction.
Q3. Write two observation that indicate a chemical reaction.
Answer- (i) change in colour (ii) formation of gas
Q4. What is a balanced chemical equation?
Answer- A chemical equation in which the number of atoms of each element is equal on both sides of the equation.
Q5. Why should chemical equations be balanced?
Answer – Chemical equation should be balanced to satisfy the law of conservation of mass which states that
mass is neither created nor destroyed in a chemical reaction.
Q6. What is a combination reaction?
Answer – A reaction in which two or more substances combine to form a single product.
Q7. What is a decomposition reaction?
Answer- A reaction in which one compound breaks into two or more simpler substances.
Q8. What is displacement reaction?
Answer- A reaction in which a more reactive metal displaces a less reactive metal from its compound.
Q9. What is a double displacement reaction?
Answer – A reaction in which ions are exchanged between two compounds.
Q10. What is oxidation?
Answer – Addition of oxygen or removal of hydrogen from a substance is called oxidation.
Q11.Give one example of an exothermic reaction.
Answer – CH4 + 2O2 →2H2O +heat
Q12. Give one example of endothermic reaction.
Answer – CaCO3 →CaO +CO2
Related Topics
1. Chemical Reactions and Equations Solutions
2. Chemical Reactions and Equations MCQs
3. Acids , Bases and Salts Quick Revision Notes
4. Metals and Non-Metals Quick Revision Notes
5. Carbon and its Compounds Quick Revision Notes