Chemical equation
- It is symbols that describe a chemical reaction and indicate identities and relative amount of reactants and products.
Coefficient
- Numeral used in a chemical equation to indicate relative amounts of reactants or products.
I will show you how reactions are written as I explain with an example. There is our first tables that are show 2 ways writing equations.
| Representation | Reactants | Yield (or "produce") | product |
| Formula equation | H2 + O2 | -------> | H2O |
| Molecular models |  +  |
-------> |  |
In reactant there are 2 hydrogen atoms and 2 oxygen atoms but after produce there are 2 hydrogen atoms and 1 oxygen atom. In order to be chemical equation you would need 2 water molecules, each containing one oxygen atom. So that would be 2 oxygen atoms each in reactant and product. So you can write number 2 in front of the formula for the water molecule and this way are called coefficient.
H atoms
Reactants: 2
Products: 4
O atoms
Reactants: 2
Products: 2
Nothing is problem, now? Wellˇ¦ the amount of atom of hydrogen was balanced just before we added one more water molecule but now we got 2 more hydrogen atom, or 1 more hydrogen molecule, in product. Balancing equation would be prefect by adding 2 more hydrogen atoms, which means adding 1 more hydrogen molecule, in reactant. Therefore, we get balanced equation that no atoms are left unaccounted or being violated. Here is chemical equation for water.
2H2 + O2 ---------> 2H2O.
Number In red = Coefficient (Number of formula units in reaction)
Number in blue = Subscript (Number of atoms in formula unit)
Things to know when you write the chemical equation.
1. When trying to write to correct equation, DO NOT changes the products or reactants either by adding new ones or by changing the subscripts and identities of the formulas in the equation.
2. You should never insert a coefficient between the elements in a chemical formula.
3. No new reactants or products are being added.
4. Inserting coefficients to satisfy the law of conversation of mass is referred to as ˇ°Balancing Equation.ˇ±
5. Check your equation that is balanced or not after you wrote the equation.
What is a chemical reaction?
How can reaction be used?
