, CHEMISTRY CHEMICAL REACTIONS AND EQUATIONS
Chemical Reactions and Equations
When a chemical change occurs, a chemical reaction takes place.
Chemical Equation
The simple form of representation of a chemical reaction in words is known as a word equation.
(Reactants) (Products)
Representation of a chemical reaction with the help of chemical formulae is called a chemical
equation.
(Reactants) (Products)
Writing Chemical Equations
In a chemical reaction, the reactants are written on the left hand side and the products on the right
hand side of the equation.
An arrow (→) pointing towards the products is inserted between the reactants and the products. It also
represents the direction of the reaction.
A single arrow (→) indicates the direction in which the reaction proceeds.
A double arrow ( ) indicates a reversible reaction, i.e. the products recombine to form the
reactants.
A plus sign (+) is inserted between two or more reactants or products formed.
If reactions are carried out under specific conditions of temperature, pressure, catalyst etc., then these
conditions are mentioned on the arrow.
The chemical equation can be made more informative by mentioning the physical states of the
reactants and products.
If gas is liberated as a product then it is represented by an arrow pointing upwards (↑). If the product
formed is in the form of a precipitate, it is represented by an arrow pointing downwards (↓).
Balancing the Chemical Equations
In a balanced chemical equation, the total number of atoms of each element of the reactants on the
left hand side of the equation is equal to the number of atoms of the products formed on the right hand
side of the equation.
The total mass of the reactants is equal to the total mass of the products or the number of atoms of
each element before the reaction and after the reaction is equal.
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Chemical Reactions and Equations
When a chemical change occurs, a chemical reaction takes place.
Chemical Equation
The simple form of representation of a chemical reaction in words is known as a word equation.
(Reactants) (Products)
Representation of a chemical reaction with the help of chemical formulae is called a chemical
equation.
(Reactants) (Products)
Writing Chemical Equations
In a chemical reaction, the reactants are written on the left hand side and the products on the right
hand side of the equation.
An arrow (→) pointing towards the products is inserted between the reactants and the products. It also
represents the direction of the reaction.
A single arrow (→) indicates the direction in which the reaction proceeds.
A double arrow ( ) indicates a reversible reaction, i.e. the products recombine to form the
reactants.
A plus sign (+) is inserted between two or more reactants or products formed.
If reactions are carried out under specific conditions of temperature, pressure, catalyst etc., then these
conditions are mentioned on the arrow.
The chemical equation can be made more informative by mentioning the physical states of the
reactants and products.
If gas is liberated as a product then it is represented by an arrow pointing upwards (↑). If the product
formed is in the form of a precipitate, it is represented by an arrow pointing downwards (↓).
Balancing the Chemical Equations
In a balanced chemical equation, the total number of atoms of each element of the reactants on the
left hand side of the equation is equal to the number of atoms of the products formed on the right hand
side of the equation.
The total mass of the reactants is equal to the total mass of the products or the number of atoms of
each element before the reaction and after the reaction is equal.
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2
