Chapter 3 F4 : The Mole Concept, Chemical Formula & Equations
1. Relative Atomic Mass (RAM) & Relative Molecular Mass (RMM)
Relative atomic mass (RAM) Relative molecular mass (RMM) Relative formula mass (RFM)
Average mass of an atom of the Average mass of the molecule Relative mass of an ionic
element compared to 1/12 of the compared to 1/12 of the mass of substance.
mass of one carbon-12 atom. one carbon-12 atom. Uses concept of relative mass in
ionic substances.
Formula : Formula : To calculate :
Average mass of one Average mass of one Sum up all RAM of all atoms in
RAM = atom of element RMM = molecule the formula of the ionic
1/12 x Mass of 1 1/12 x Mass of 1 substance.
Carbon-12 atom Carbon-12 atom
Can be calculated by adding up
all RAM of all atoms in molecule.
Why Carbon-12 is used as standard atom? 2. The Mole Concept.
• Solid at room temperature What is mole?
• Easy to handle • Symbol : mol ; SI unit of amount of substance.
• Combines easily with other elements, • 1 mole of substance = 6.0221 x 1023 entities of
found in most substances. substance.
• Major isotopes with 99% of abundance, • This fixed value is known as Avogadro constant
makes it exactly 12.0 or Avogadro Number, NA which are expressed
in mol-1.
• Avogadro number, NA = 6.02 x 1023 particles
2. The Mole Concept [CONT.]
NUMBER OF MOLES &
NUMBER OF PARTICLES MASS OF SUBSTANCES VOLUME OF GASES
• Number or moles, n = • Molar mass : mass of 1 mole • Molar volume : Volume
Number or particles / NA of substance occupied by 1 mol of a gas.
• Value of molar mass = • Depends on condition :
relative mass of the - At STP : 22.4 dm3mol-1
substance. - At room : 24 dm3
• Eg : RMM of H2O is 18, the
molar mass = 18.
3. Chemical Formula
Definition : representation of
chemical substance using alphabet
to represent atom & subscript
number to show the number of
each type of atoms found in the
substance.
1. Relative Atomic Mass (RAM) & Relative Molecular Mass (RMM)
Relative atomic mass (RAM) Relative molecular mass (RMM) Relative formula mass (RFM)
Average mass of an atom of the Average mass of the molecule Relative mass of an ionic
element compared to 1/12 of the compared to 1/12 of the mass of substance.
mass of one carbon-12 atom. one carbon-12 atom. Uses concept of relative mass in
ionic substances.
Formula : Formula : To calculate :
Average mass of one Average mass of one Sum up all RAM of all atoms in
RAM = atom of element RMM = molecule the formula of the ionic
1/12 x Mass of 1 1/12 x Mass of 1 substance.
Carbon-12 atom Carbon-12 atom
Can be calculated by adding up
all RAM of all atoms in molecule.
Why Carbon-12 is used as standard atom? 2. The Mole Concept.
• Solid at room temperature What is mole?
• Easy to handle • Symbol : mol ; SI unit of amount of substance.
• Combines easily with other elements, • 1 mole of substance = 6.0221 x 1023 entities of
found in most substances. substance.
• Major isotopes with 99% of abundance, • This fixed value is known as Avogadro constant
makes it exactly 12.0 or Avogadro Number, NA which are expressed
in mol-1.
• Avogadro number, NA = 6.02 x 1023 particles
2. The Mole Concept [CONT.]
NUMBER OF MOLES &
NUMBER OF PARTICLES MASS OF SUBSTANCES VOLUME OF GASES
• Number or moles, n = • Molar mass : mass of 1 mole • Molar volume : Volume
Number or particles / NA of substance occupied by 1 mol of a gas.
• Value of molar mass = • Depends on condition :
relative mass of the - At STP : 22.4 dm3mol-1
substance. - At room : 24 dm3
• Eg : RMM of H2O is 18, the
molar mass = 18.
3. Chemical Formula
Definition : representation of
chemical substance using alphabet
to represent atom & subscript
number to show the number of
each type of atoms found in the
substance.
