Chemical Equations
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Transcript of Chemical Equations
Chemical Equations
At the end of this lesson, you should be able to..
construct balanced chemical equations with state symbols.
An equation represents what occurs in a chemical reaction.
Can be written using words or chemical formulae
Word Equation:
Sodium + Hydrochloric acid Sodium chloride + Hydrogen
Chemical Equation:
2 Na + 2 HCl 2 NaCl + H2
2Na + 2HCl 2NaCl + H2
(s) (aq)
(aq)
(g)
Reacting substances,
or reactants are on the left-hand side of
the equation.
Products or substances formed are on the right-hand side
of the equation.
The arrow means ‘react to form’ The reaction proceeds from left to right.
Sodium and hydrochloric acid react to form sodium chloride and hydrogen.
Step 1: Write down the chemical formulae of the reactants and products.
Step 2: Balance the equation.
Step 3: Write down the state symbols.
In a chemical reaction, substances are changed into other substances. No matter is created nor destroyed.
i.e. the number of atoms before and after the reaction remains the same.
Marks can be penalized if you give the wrong state symbols, even when the
question did not ask for it!
Liquid state (l): Pure substance that is in liquid form
Aqueous state (aq): Substance dissolved in water
Is the substance soluble in water?
Many ionic compounds are soluble in water.
Most covalent compounds are not soluble in water.
SOLUBLE covalent compounds
Magnesium reacts with sulphuric acid to form magnesium sulphate and hydrogen.
Sulfuric acid reacts with sodium hydroxide to form sodium sulfate and water.
Soluble InsolubleAll Sodium All PotassiumAll Ammonium
All nitrates
Sulphates except
Chlorides exceptIodides exceptBromides except
Carbonates except SPAHydroxides except SPAOxides except SPA
PbSO4 and BaSO4
PbCl2 and AgClPbI2 and AgIPbBr2 and AgBr