QUANTITATIVE ASPECTS OF CHEMICAL CHANGE
Stoichiometric Calculations
1. Write down the balanced equation
2. Identify the substances needed
3. Convert the given information to moles
4. Determine the number of moles using the mole ratio
5. Convert back to mass, volume or concentration as needed
The mole and Avogadro’s constant
Mole is the SI unit used to indicate amount of substance
The amount of a substance containing as many particles as there
are atoms in 12g of carbon-12
This number is Avogadro’s constant (NA) (6,021023)
Number of particles = nNa
The mole and mass
The relative atomic mass of an element is a figure comparing the
real mass of one atom of the element with 112of the mass of the
carbon-12 atom which has a mass of 12 atomic mass units
Isotopesatoms of the same element but with different numbers of
neutrons (same atomic number, different mass number)
Molar mass of the substancethe relative atomic mass of an
element or the relative molecular/ formula mass of a compound in
grams indicates one mole of the specific element or compound
n=mMwhere n= number of moles, m=mass, M= molar mass
Molar volume of gases
Avogadro’s Lawequal volumes of different gases at the same
temperature and pressure contain the same number of moles of
gas
Molar gas volumeone mole of any gas at STP occupies a volume
of 22,4 dm3
Concentration of solutions
c=nv where c= concentration, n= number of moles, v= volume of
solution
Unit = moldm-3
Standard solutiona solution of which the exact concentration is
known
Stoichiometric Calculations
1. Write down the balanced equation
2. Identify the substances needed
3. Convert the given information to moles
4. Determine the number of moles using the mole ratio
5. Convert back to mass, volume or concentration as needed
The mole and Avogadro’s constant
Mole is the SI unit used to indicate amount of substance
The amount of a substance containing as many particles as there
are atoms in 12g of carbon-12
This number is Avogadro’s constant (NA) (6,021023)
Number of particles = nNa
The mole and mass
The relative atomic mass of an element is a figure comparing the
real mass of one atom of the element with 112of the mass of the
carbon-12 atom which has a mass of 12 atomic mass units
Isotopesatoms of the same element but with different numbers of
neutrons (same atomic number, different mass number)
Molar mass of the substancethe relative atomic mass of an
element or the relative molecular/ formula mass of a compound in
grams indicates one mole of the specific element or compound
n=mMwhere n= number of moles, m=mass, M= molar mass
Molar volume of gases
Avogadro’s Lawequal volumes of different gases at the same
temperature and pressure contain the same number of moles of
gas
Molar gas volumeone mole of any gas at STP occupies a volume
of 22,4 dm3
Concentration of solutions
c=nv where c= concentration, n= number of moles, v= volume of
solution
Unit = moldm-3
Standard solutiona solution of which the exact concentration is
known
