Chemistry: Animation, Video, and Laboratory Activity

For example, the equation for the reaction of Hydrogen with oxygen to form water.
2H2 + O2 -> 2H2O
The formula for the reactants are written to the left arrow, and the formulas for the products are written to the right.
The arrow is read as “gives”, “produces”, “yields”, or “ forms”.
A plus sign on the left side of an equation means ‘reacts with’.
Coefficient of reaction is the ratio between a substances involved in the reaction.
Look at this reaction :
2H2 + 1 O2 -> 2H2O
For example above, coefficient reaction shows that 2 molecules of Hydrogen react with one molecule of oxygen to form 2 molecules of water.
Since matter cannot be created or destroyed in a chemical reaction, a chemical equation must have the same number of atoms in the products as there are in the reactants.
From the example above, we can look that the number of hydrogen atom in the left side is same as the right one, is 4. Either, the number of oxygen atom in the left side is same as the right one, is 2. This equation is called balanced equation
For balancing the chemical equation, can’t determine by change index number.
Index number determines the formula of substances, so that if we change index number as like as we change the kind of substances.
Coefficient number related with a number of substances, so if we change coefficient number that we only change the number of substances.
2H2 + O2 -> 2H2O
This reaction can’t be balanced by change index O in H2O become 2, so the reaction :
2H2 + O2 -> H2O2

There are 3 steps to write a balanced equation, they are:
• Write the word equation consist of name and the form of reactants and products.
• Write the formula equation consists of a chemical formula of reactants and products complete with the phase.
• Balancing, gives a correct coefficient so that it has the same number of atoms in the products and reactants.
Example :
a. Aluminum reacts with sulfuric acid solution to form aluminum sulfate solution and hydrogen gases. Balanced the reaction!
Answer :
Step 1 : write the word equation
aluminum + sulphuric acid solution à aluminum sulphate solution + hydrogen gases
Step 2 : write the formula equation
Al(s) + H2SO4(aq) ->à Al2(SO4)3(aq)+ H2(g)
Step 3 : balancing
2Al(s) + 3H2SO4(aq) -> Al2(SO4)3(aq)+ 3H2(g) Balance

Balancing the chemical equation
1 Determine one of substances (a substances which has a complex chemical formula). Give assign 1 in it. And the other, you can give assign with other characters.
2 Balance a substances related with a substances which given assign 1 first.
3 Balance the other substances. It will easier if oxygen atom is balanced first.
Example :
b. The reaction of aluminum and hydrochloric acid solution to form aluminum chloride solution and hydrogen gases
Al(s) + HCl(aq) -> AlCl3(aq)+ H2(g) not balanced
Step 1 : determine coefficient of AlCl3 = 1, and letter for the other
aAl(s) + bHCl(aq) -> 1AlCl3(aq)+ cH2(g)
Step 2 : balance aluminum and chlorine atom
The number of Al atom in the left side = a, while in the right side = 1, so a = 1
The number of Cl atom in the left side = b, while in the right side = 3, so b = 3
1Al(s) + 3HCl(aq) ->à 1AlCl3(aq)+ cH2(g)
Step 3 : balance Hydrogen atom
The number of hydrogen atom in the left side =3
In the right side = 2c, so c = 1,5
1Al(s) + 3HCl(aq) -> 1AlCl3(aq)+ 1,5H2(g)
Final balance equation : 2Al(s) + 6HCl(aq) -> 2AlCl3(aq)+ 3H2(g)