CHEMICAL CHEMICAL EQUATIONSEQUATIONS

Learning Objective:•To write and explain chemical equations.

CHEMICAL CHEMICAL EQUATIONSEQUATIONS

Learning Outcomes•Good if you are able to interpret word equations.•Even better if you are able to use molecular models to represent reactions.•Great if you can write word equations and use as part of an explanation.•Out of this world if you can write balanced symbol equations.

WORD EQUATIONS

Word equations are a short way of describing reactions

They are written in the format:

REACTANTS

The substances that react together

PRODUCTS

The substances that are made

WORD EQUATIONS

example

Identify the reactants

Write them on the left hand side

Identify the products

Write them on the right hand side

magnesium + oxygen

magnesium oxide

When magnesium burns it reacts with the oxygen in the air to make magnesium oxide

WORD EQUATIONSexample

Identify the reactants

Write them on the left hand side

Identify the products

Write them on the right hand side

sodium + chlorine sodium chloride

Use names only!

White crystals of sodium chloride are formed when green chlorine gas is reacted with sodium metal.

WORD EQUATIONS

zinc + copper

zinc sulphate + copper

Zinc reacts with blue copper sulphate solution to form colourless zinc sulphate and copper

use full name

sulphate

WORD EQUATIONS

calcium carbonate + hydrochloric acid calcium chloride + carbon dioxide

Reactants on left of arrow, all products on the right of the arrow

calcium carbonat

e

When calcium carbonate is added to hydrochloric acid, the solution bubbles making calcium chloride, water and carbon dioxide

water

hydrochloric acid

calcium chloride

carbon dioxide

++

+water

FORMULA EQUATIONS

These equations use formula instead of names

The formula are often given to youThey are also

written in the format:

REACTANTS PRODUCTS

They need to be balanced.

There needs to be the same number of each type of atom on both sides of the equation

FORMULA EQUATIONS

When magnesium burns it reacts with the oxygen in the air to make magnesium oxide

Mg + O2

MgO Oxygen comes bonded to magnesium

22

FORMULA EQUATIONS

If sodium (Na) is added to water (H2O) sodium hydroxide (NaOH) and hydrogen gas (H2) are formed

Na + H2O NaOH + H2

need another hydrogen

but a hydrogen comes joined to an oxygen and a hydrogen

need an oxygen and another hydrogen

Can get these from hereand get a sodium

2 2 2

Try TheseMg + O2

Zn + HCl

Fe + Cl2

NaOH + HCl

CH4 + O2

Ca + H2O

NaOH + H2SO4

CH3OH + O2

MgO

ZnCl2 + H2

FeCl3

NaCl + H2O

CO2 + H2O

Ca(OH)2 + H2

Na2SO4 + H2O

CO2 + H2O

2

2

2 3

2

2

2

2 3

2

2

2

2

2 4