2.1.3 Amount of substances
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the mole is…
the amount of substance in grams that has the same number of particles as there are atoms in 12g of carbon 12
relative atomic mass is…
the average mass of an atom compared to the mass of one atom of carbon 12
relative molecular mass is …
the average mass of a molecule compared to one twelfth of the mass of one atom of carbon 12
molar mass is…
the mass in grams of one mole of substance (gmol-1)
avogadro’s constant
the number of particles in one mole
mass =
n x Mr
no of particles =
n x 6.02 x 10^23
volume in (dm^3)
n/C
moldm^-3 can be made into gdm^-3 by…
multiplying by the Mr
avogadro’s number shows …
that there are 6.02 x 10^23 atoms in 12g of carbon 12
xH2O means …
water of crystallisation
salts that have water removed are …
anhydrous
empirical formula is…
the simplest whole number ratio of atoms in a compound
molecular formula is …
the actual number of atoms in a compound
how to work out the factor of an empirical formula
factor = mr of molecular formula / mr of empirical formula
to work out the molecular formula you …
empirical formula x factor
ideal gas equation
P(Pa)V = nRT
T=
273 +/- ?°C
R =
8.31
V (m^3) =
cm^3 / 10^6 or dm^3 / 1000
1 mole of any gas at room temp and room pressure =
25°C and 24dm^3
gas volume (dm^3) =
n x 24 (or 24,000 if answer is wanted in cm^3)
% yield =
actual yield / theoretical yield x 100
name two ways % yield can be lowered
• incomplete reactions • side reactions • losses during purification • transfer of substances