How to write chemical equations and balancing equations

1. Writing and Balancing
Chemical Reactions

2. Chemical Equation
• Can illustrate the formulas
and quantities of reactants
and products in a chemical
reaction

3. Chemical equation can show the
following:
• the chemical reactants that
enter into a reaction;
• the products that are formed by
the reaction; and
• the number of moles of each
substance used and each
substance produced.

4. 2Na (s) + Cl2 (g) 2NaCl (s)
“Table Salt”

5. Guidelines in Writing Chemical
Equations
• Elements that exist as diatomic molecules are
written as follows: H2 N2, O2, F2, Cl2, Br2 and I2
• The reactant/s are written on the left side of
the equation while the product/s are written
on the right side of the equation.
2NaCl (s) Cl2 (g) 2NaCl (s)+
Reactants Product

6. Guidelines in Writing Chemical
Equations
• The sign, ,means “yields” and shows the
direction of the reaction. A double arrow, ,
means that the reaction is reversible.
• The law of conservation of mass holds for
every chemical reaction and therefore chemical
equation
• The physical state of the substance may also be
indicated using the following s, l, g and aq
2NaCl (s) Cl2 (g) 2NaCl (s)+

7. Balancing of Chemical Equation
by Inspection
Always remember the
Law of Conservation of Mass
What if the equation is not balanced?
CH4(g) + O2 (g) CO2 (g) + H2O (l)

8. Steps in Balancing
1. Write the formula of the substances.
2. Count the number of atoms in each
element on each side of the
equation.
3. Adjust the coefficient.
4. Check if the number of atoms each
elements is the same on both sides.

9. Sample Problem # 1
Balance the equation for
reaction between iron and
oxygen to give iron (III)
oxide.

10. Sample Problem # 2
Give the balanced equation
for the reaction between
aluminum metal and
hydrochloric acid forming
aqueous aluminum chloride and
hydrogen gas.

11. Self-Check (Exercise)
•Magnesium reacts with
nitrogen gas forming
solid magnesium nitride.
Mg3N2