chem f4c3

Avogadro constant

6.02 x 10^23

Relative Atomic Mass (RAM)

The average mass of an atom of an element relative to 1/12 of the mass of one carbon-12 atom

why carbon-12?

exist as solid, easy to handle + found in most substances +

it is the most abundant carbon isotope

n=

MV/1000

n=

no of particle/avogadro's constant

n=

mass/molar mass

n=

volume/molar volume

Chemical Formula

A representation of a chemical substance using alphabets to represent the atoms and subscript numbers to show the numbers of each type of atoms found in the elementary entities of the substance.

Empirical Formula

Chemical formula that shows the simplest whole number ratio of atoms of each element in a compound.
Examples: • Glucose: CH₂O • Ethene: CH₂

Molecular Formula

Chemical formula that shows the actual number of atoms of each element in a compound.
Examples: • Glucose: C₆H₁₂O₆ • Ethene: C₂H₄

Chloride ion
Bromide ion
Iodide ion
Hydroxide ion
Nitrate ion
Manganate (VII) ion
Oxide ion
Sulphate ion
Carbonate ion Dichromate (VI) ion
Thiosulphate ion
Phosphate ion

Cl⁻
Br⁻
I⁻
OH⁻
NO₃⁻
MnO₄⁻
O²⁻
SO₄²⁻
CO₃²⁻
Cr₂O₇²⁻
S₂O₃²⁻
PO₄³⁻

Rub Mg with sand paper before experiment

Remove oxide layer

Close crucible with lid when magnesium starts burning

Prevent loss of white fumes (MgO)

Lift the lid slightly from time to time

Allow oxygen to enter crucible and react with magnesium

Repeat heating, cooling and weighing processes until constant mass is obtained

To ensure all magnesium is changed into magnesium oxide

This method is suitable to determine empirical formula of magnesium oxide

Magnesium is reactive towards oxygen

This method is not suitable to determine empirical formula of copper (II) oxide

Copper is less reactive towards oxygen