# Writing a balanced chemical equation

In these lessons, we will learn how to write a balanced chemical equation given the word equation. We have more lessons on the rules for balancing chemical equations.

Related Topics: More Chemistry Lessons

### Chemical Equation

A chemical equation shows the overall change of reactants to products in a chemical reaction.

Sometimes, state symbols are required to indicate the physical states of the substances in a chemical reaction.

 Physical state State symbol Solid s Liquid l Gas g Aqueous Solution aq

Here are some simple covalent formulas that you will find useful to remember
Water H2O
Carbon Dioxide CO2
Ammonia NH3
Hydrogen H2
Oxygen O2
Nitrogen N2
Sulfur Dioxide or Sulphur Dioxide SO2
Methane CH4

Here are some simple ionic formulas that you will find useful to remember
Sodium Chloride NaCl
Calcium Chloride CaCl2
Magnesium Oxide MgO
Hydrochloric Acid HCl
Sulfuric Acid or Sulphuric Acid H2SO4
Nitric Acid HNO3
Sodium Hydroxide NaOH
Potassium Hydroxide KOH
Calcium Hydroxide Ca(OH)2
Calcium Carbonate CaCO3
Aluminum Oxide Al2O3
Iron Oxide Fe2O3

### Conversion of word equation to chemical equation

Example:

In a precipitation reaction, sodium hydroxide solution is mixed with iron(II) chloride solution. Sodium Chloride solution and insoluble iron(II) hydroxide are produced. Write a balanced chemical equation including the state symbols.

Solution:

Step 1: Identify reactants and products and place them in a word equation,

sodium hydroxide + iron(II) chloride → sodium chloride + iron(II) hydroxide

Step 2: Convert the chemical names into chemical formulas. Place them based on the chemical equation and write the state symbols.

Step 3: Balance the chemical equation.

2NaOH(aq) + FeCl2(aq) → 2NaCl(aq) + Fe(OH)2(s)

Example:

Write a balanced chemical equation for

Sodium(s) + hydrochloric acid(aq) → sodium chloride(aq) + hydrogen(g)

Solution:

Step 1: Convert the chemical names into chemical formulas. Place them based on the chemical equation and write the state symbols.

Step 2: Balance the chemical equation.

2Na(s) + 2HCl(aq) → 2NaCl(aq) + H2(g)

How to write a balanced chemical equation from a word equation?
When compounds react, they are chemically changed into new compounds. Every chemical change can be communicated symbolically using a chemical equation. Chemical equations combine formulas with other symbols to show what changes takes place.

Example:
Aluminum + Iron(III) oxide → Aluminum oxide + Iron
Oxygen + Hydrogen → Water
Methane + Oxygen → Carbon Dioxide + Water
Butane + Oxygen → Carbon Dioxide + Water

How to interpret chemical symbols and write simple balanced equations?
Each element is represented by a different symbol.
All these symbols are in the periodic table.
We can use these symbols to show molecules of compounds, and they can show us the ratio of the different elements which combine to form compounds.

Practice writing chemical equations from word problems and balancing equations
Examples:
1. Ammonium nitrate decomposes explosively to form nitrogen, oxygen, and water vapor.
2. Dinotrogen tetrahydride reacts with oxygen to produce nitrogen and water.
3. Lead(II) nitrate reacts with sodium iodide to create lead (II) iodide and sodium nitrate.
4. Phosphorous reacts with oxygen gas to produce diphosphorous pentoxide.
5. When calcium comes in contact with water, calcium hydroxide and hydrogen gas is produced.
6. When hexane (C6H24) reacts with oxygen a combustion reaction occurs. This reaction produces carbon dioxide and water.
7. Sodium hydroxide reacts with iron (III) nitrate to create a precipitate of iron (III) hydroxide in a solution of sodium nitrate.
8. Mercury (II) oxide decomposes to produce mercury and oxygen.
9. Zinc hydroxide reacts with phosphoric acid (H3PO4) to produce zinc phosphate and water.
10. Sulfur dioxide and oxygen combine to produce sulfur trioxide.

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