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.
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.
The following table gives the physical states and the state symbols used in chemical equations: solid, liquid, gas, aqueous.
The following table gives the valency of some common ions. This table can be used to help you work out the chemical formula of the reactants and products.
Here are some simple covalent formulas that you will find useful to remember:
Here are some simple ionic formulas that you will find useful to remember:
The following diagram shows how to write a chemical equation. Scroll down the page for more examples and solutions.
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.
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)
Write a balanced chemical equation for
Sodium(s) + hydrochloric acid(aq) → sodium chloride(aq) + hydrogen(g)
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)
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.
Aluminum + Iron(III) oxide → Aluminum oxide + Iron
Oxygen + Hydrogen → Water
Methane + Oxygen → Carbon Dioxide + Water
Butane + Oxygen → Carbon Dioxide + Water
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.
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