A complete chemical equation represents the reactants, products and their physical
>A chemical equation is balanced so that the numbers of atoms of each type involved
in a chemical reaction are the same on the reactant and product sides of the
equation. Equations must always be balanced.
Fe + H2O —> Fe3O4 + H2 (unbalanced equation)
3Fe + 4H2O —>Fe3O4 + 4H2 (balanced equation)
The balanced Eq. becomes
3Fe(s) + 4H2O(g) —> Fe3O4(s) + 4H2(g)
Sometimes the reaction conditions, such as temperature, pressure, catalyst, etc., for the reaction are indicated above and/or below the arrow in the equation
TYPES OF CHEMICAL REACTIONS—
>In a combination reaction two or more substances combine to form a new single substance.
Formation of water from H2(g) and O2(g)
2H2(g) + O2(g) —> 2H2O(l)
Decomposition reactions are opposite to combination reactions. In a decomposition reaction, a single substance decomposes to give two or more substances.
white silver chloride turns grey in sunlight. This is due to the decomposition of silver chloride into silver and chlorine by light.
2AgCl(s) —>2Ag(s) + Cl2(g)
Silver bromide also behaves in the same way.
2AgBr(s) —>2Ag(s) + Br2(g)
The above reactions are used in black and white photography.
Reactions in which heat is given out along with the products are called exothermic reactions.
examples of exothermic reactions are –
Burning of natural gas
CH4(g) + 2O2 (g) —> CO2 (g) + 2H2O (g)
Reactions in which energy is absorbed are known as endothermic reactions.
>When an element displaces another element from its compound, a displacement reaction occurs.
>Two different atoms or groups of atoms (ions) are exchanged in double displacement reactions
>Precipitation reactions produce insoluble salts
The chemical reaction in which a white coloured substance which is insoluble in water (precipitate) is formed then it is known as precipitation reaction
In this reaction Barium sulphate is a white colour precipitate and it is insoluble in water.
Oxidation is the gain of oxygen or loss of hydrogen
Reduction is the loss of oxygen or gain of hydrogen
CBSE 10th Standard Science
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CBSE 10th Standard Science Syllabus and Revision Notes
- Class 10 Chapter 1 – Chemical Reactions and Equations
- Class 10 chapter 2 – Acids, Bases and Salts
- Class 10 Chapter 3 – Metals and Non Metals
- Class 10 Chapter 4 – Carbon and its Compounds
- Class 10 Chapter 5 – Periodic Classification of Elements
- Class 10 Chapter 6 – Life Processes
- class 10 chapter 7 – Control and Coordination
- Class 10 Chapter 8 – How do Organisms Reproduce?
- Class 10 Chapter 9 – Heredity and Evolution
- Class 10 Chapter 10 – Light – Reflection and Refraction
- Class 10 Chapter 11 – The Human Eye and the Colourful World
- Class 10 Chapter 12 – Electricity
- Class 10 Chapter 13 – Magnetic Effects of Electric Current
- Class 10 Chapter 14 – Sources of Energy
- Class 10 Chapter 15 – Our Environment
- Class 10 Chapter 16 – Management of Natural Resources