Chemical Equation

Chemical-Equation_Chem-Eng.21

Chemical equations usually do not come already balanced. Making sure they are balanced must be done before the equation can be used in any chemically meaningful way.
All chemical calculations you will see in other units must be done with a balanced equation.
IMPORTANT DEFINITION: A balanced equation has equal numbers of each type of atom on each side of the equation.
The Law of Conservation of Mass is the rationale for balancing a chemical equation. The law was discovered by Antoine Laurent Lavoisier (1743-94) and this is his formulation of it, translated into English in 1790 from the Traité élémentaire de Chimie (which was published in 1789):

"We may lay it down as an incontestible axiom, that, in all the operations of art and nature, nothing is created; an equal quantity of matter exists both before and after the experiment; the quality and quantity of the elements remain precisely the same; and nothing takes place beyond changes and modifications in the combination of these elements."

A less wordy way to say it might be:

"Matter is neither created nor destroyed."

Therefore, we must finish our chemical reaction with as many atoms of each element as when we started.

CHEMICAL-EQUATION

There are 5 steps:

1.Write the correct formula(s) for the reactants on the left side and the correct formula(s) for the product(s) on the right side of the equation.

Ethane bereaksi dengan oxygen membentuk carbon dioxide and air

C2H6 + O2==>CO2 + H2O

2.Change the numbers in front of the formulas (coefficients) to make the number of atoms of each element the same on both sides of the equation. Do not change the subscripts.

2C2H6 NOT C4H12

3.Start by balancing those elements that appear in only one reactant and one product.

C2H6 + O2==>CO2 + H2O

C2H6 + O2==>2CO2 + H2O

C2H6 + O2==>2CO2 + 3H2O

4.Balance those elements that appear in two or more reactants or products.

C2H6 + O2==>2CO2 + 3H2O