The Chemical equation is the symbolic representation of a chemical reaction.
Or
The method of representing a chemical reaction with the help of symbol and formulae of the substance evolved it is known as chemical equation.
• Symbol and formula of the reactant and product are used for the same.
Example: Word equation:
Hydrogen + Oxygen —> Water
• Chemical equation:
2H2 + O2 —-> H2O
• Example : Reaction of burning methane gas can be written in word as;
Methane + Oxygen —> Carbon dioxide + Water
How to make the reaction more informative:
• By indicating physical state of the equation:
The physical state of the reactant and product can be represented by using symbol.
i) Solid is indicated by the symbol of (s).
S ——> Solid
2Mg (s) + O2 = 2MgO (s)
ii) Liquid is indicated by the symbol (l).
l ——-> Liquid
2H2 (g) + O2 (g) –> H2O (l)
iii) Gas in indicated by the symbol of (g).
g. ——-> Gas
Zn(s) + H2SO4 (l) –> H2 (g) + ZnSO4
iv) Aqueous solution (made In water) is indicated by (aq).
aq ——–> Aqueous
AgNO3 (aq) + NaCl (aq) —> AgCl + NaNO3 (Aq)
Precipitated can be represented by arrow pointing downward (↓ ) instead of using symbol s.
- In the same way gaseous state of evolve gas can be represented by the arrow pointing upwards (↑) instead of symbol g.
- By indicated the condition under the reaction takes place:
If heat is required for the reaction to takes place, then the heat sign Delta ( ∆)
is put over the arrow of the equation.
• The specific conditions reaction like temperatures or pressure catalyst etc. Are written to the above or below the arrow of chemical equation.
• Evolution of heat and absorption of heat can be written as (+heat) on the right
hand sight or left hand sight of the equation. There are two type of reaction
occurs on the basis of heat change
i) Exothermic reaction:
Those reaction in which heat is evolved are known as exothermic reaction . Exothermic reaction can be represented by writing + heat or + heat energy or + energy on the product side of the equation.
Example Respiration, and burning of carbon in presence of air.
C + O2 —> CO2 + Heat
ii) Endothermic Reaction:
Those reaction in which heat is absorbed are known as Endothermic Reaction.
An endothermic Reaction by indicated by writing + Heat or Heat energy Or just + energy on the reactant side of the equation.
Example: photosynthesis Reaction
6CO2 + 6H2O + Heat –> C6H12O6 + 6O2
Question Answer:
1) What is chemical equation?
Answer: The Chemical equation is the symbolic representation of a chemical reaction.
2) Give example of word or formulae chemical equation?
Answer: Example: Word equation:
Hydrogen + Oxygen —-> Water
- Chemical equation:
2H2 + O2 –> H2O
3) How to make Reaction more informative by indicated physical state of Reaction?
Answer:
• By indicating physical state of the equation:
The physical state of the reactant and product can be represented by using symbol.
i) Solid is indicated by the symbol of (s).
S ——> Solid
2Mg (s) + O2 = 2MgO (s)
ii) Liquid is indicated by the symbol (l).
l ——-> Liquid
2H2 (g) + O2 (g) –> H2O (l)
iii) Gas in indicated by the symbol of (g).
g. ——-> Gas
Zn(s) + H2SO4 (l) –> H2 (g) + ZnSO4
iv) Aqueous solution (made In water) is indicated by (aq).
aq ——–> Aqueous
AgNO3 (aq) + NaCl (aq) —> AgCl + NaNO3 (Aq)
4) Write about heat absorption Reaction?
Answer: Endothermic Reaction:
Those reaction in which heat is absorbed are known as Endothermic Reaction.
An endothermic Reaction by indicated by writing + Heat or Heat energy Or just + energy on the reactant side of the equation.
Example: photosynthesis Reaction
6CO2 + 6H2O + Heat –> C6H12O6 + 6O2