Stoichiometry
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What is relative atomic mass (Ar)?
average mass of naturally occurring atoms of an element on a scale where the 12C atom has a mass of exactly 12 units
What is relative molecular mass? (Mr)
sum of the relative atomic masses
What is relative formula mass?
Relative molecular mass for ionic compounds
How can solution concentrations be expressed?
mol/dm3 or g/dm3
Moles =
Concentration x Volume
What is a mole?
the number of particles which is equal to the number of atoms in 12g of carbon 12
What is Avogadro’s constant? (3)
number of particles / atoms / ions / molecules in one mole of a substance the number of particles / molecules in 24dm3 of a gas at RTP
What is the number of particles in 24 dm3 of a gas at RTP?
6 to 6.0^23 × 10^23 atoms (Avogadro’s constant)
no. of moles =
mass of substance taken/mass of one mole of substance
What is the limiting reactant?
the one that is not in excess
How can we calculate the limiting reactant?
Calculate which reactant has the lower number of moles
Excess of substance =
moles of substance at start - moles of substance at end
n =
M/mr
concentration =
number of moles / volume
volume of gas (in dm3) =
number of moles x 24
% by mass of element in compound =
sum of Mr/ relative formula mass of compound x 100
% yield =
actual yield/predicted yield x 100
% purity =
mass of pure product/mass of impure product x 100
What are the 6 formulas you need to know?
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