IGCSE Chemistry Unit 3

tells you the way in which the atoms in a particular molecule are bonded, done by a diagram (displayed formula) or written (simplified structural formula)

displayed/diagram

simplified/written

tells you the actual number of atoms of each element in one molecule of the compound or element

E.g. H₂ has 2 hydrogen atoms, HCl has 1 hydrogen atom and 1 chlorine atom

simplest whole number ratio of the atoms of each element present in one molecule or formula unit of the compound (js simplest form)

eg in image

empirical

often has diff empirical and molecular formula

KEEP IN MIND you find the charge of elements from its grp

Grp 1-3 = 1+,2+,3+

Grp 4= transition

Grp 5-8= 3-,2-,1-

KEEP IN MIND Roman numeral next to the element tells you the charge on the ion, e.g. copper(II) ions have a charge 2+

Swap and Drop method (drop and switch)

Only add the brackets if needed

Metal

NM as 2nd name

ending changes to -ide

NM 2nd name

ending changes at -ate if the 2nd last element is bonded to a oxygen element

Mr, the total mass of a molecule

total mass of an ionic compound

Sum of all Ar values

dont forget the subscipts and brackets

measure of amount of a sub

6.02×10²³, Avogadro’s constant

mass of 1 mole of a sub

g/mol

for an element, MM=Ar

for a compound, MM=relative FM/Mr

At the same conditions of T and P, equal amounts of G occupy the same V

1 mol of a gas occupies 24 dm³ at rtp

moles=mol mass=g MM/Mr=g/mol

remeber to balance

The LR is the reactant that is used up first

when performing reacting mass calculations, the limiting reactant is always the number that should be used as it indicates the maximum possible amount of product

Amount of solute in a specific volume of solvent

a S sub dissolved in L

the L the solute is dissolved in

g/dm³ or mol/dm³

steps 1 and 4 depend on the qs

• Step 1: Find the relative formula mass of the empirical formula

• Step 2: Use the following equation:

• Step 3: Multiply the number of each element present in the empirical formula by the number from step 2 to find the molecular formula

The term used to describe the amount of product you get from a reaction

Some reactants may be left behind in the equipment

The reaction may be reversible and in these reactions a high yield is never possible as the products are continually turning back into the reactants

Some products may also be lost during separation and purification stages such as filtration or distillation

There may be side reactions occurring where a substance reacts with a gas in the air or an impurity in one of the reactants

Products can also be lost during transfer from one container to another

the recorded amount of product obtained

 theoretical yield is the amount of product that would be obtained under perfect practical and chemical conditions

compares the actual yield to the theoretical yield