Chemical Equation And Stoichiometry
Some Basic Concept Of Chemistry of Class 11
Chemical Equation And Stoichiometry
Chemical equation tell about what substances react and what substances are produced along with in formation of aggregation of the substance both and react by the use of following symbols.
Liquid - (l)
Gas - (g)
Crystalline solid - (amorph)
Solution - (Sol)
Aqueous solution – (aq.)
Precipitate - ↓
Light (gases) - ↑
Heating - Δ
According to general assumptions reactants on left hand side and products (although they are informed as per experimental facts) on right hand side in corporating on arrow → in the middle to indicate the progress of reaction [is forward] and = in the middle if equation is balanced are written.
If any physical parameters to procure the desired reaction is necessary they are indicated in the middle along the arrow or equal sign like temperature, pressure, catalyst medium etc.
As atoms neither created nor destroyed in a chemical reaction according to law of mass conservation balanced chemical equation must contain equal no of atoms for each elements across the sign of equality maintaining right chemical formula for each component of reaction system.
A balanced equation is a statement of the both qualitative and quantitative relation between reactant and products in solved in any chemical change. However it do not show the actual pair using of reaction unit its is expressed as partial equation.
We balance the equation by making the number of atoms of each element participating in the reaction the same as that appearing in the products. This can be accomplished by placing the required number stiochio-coefficient before each formula by taking consideration that subscripts in the formulas must not be altered.
Hit and Trial Method
This method as the name suggests, is not based on nay definite procedure. However, the following guidelines may be helpful.
(i) Write the skeleton equation by mentioning the symbols and formulae of the reactions and products.
(ii) If an elementary gas like H2, O2 or N2 etc. appears on either side of the equation, write the same in the atomic form.
(iii) Select the formula which contains the maximum number of atoms and start balancing.
(iv) In case the above method is not convenient, then start balancing the atoms which appear the least number of times.
(v) Balance the atoms of the elementary gas in the last.
(vi) When the balancing is complete, convert the equation into molecular form.
The balancing of a chemical equation by the above method is illustrated by the following examples.
Partial equation method
Chemical equations which involve a large number of reactants and products cannot be balanced easily by the hit and trial method. Balancing is done by another method called Partial equation method. In this method, the overall reaction is assumed to take place in several steps and each step is balanced by hit and trial method as illustrative below:
