moles 4.4
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how is the relative atomic mass calculated?
by adding the relative atomic masses for example: H2O RFM = (2x1) + 16 = 18
how do you work out the percentage by mass?
% = mass of a / RFM x 100 for example: percentage of C in C3H8 C3 / C3H8 x 100 = 81.8%
what is moles?
unit of amount how many particles there are in a substance
what’s the equation of moles?
moles = mass (g) / RFM
what’s empirical formula?
empirical formula of a substance is the simplest mole ration of elements C6H12 > CH2 > 1:2
how to calculate empirical formula and ratio:
mass RFM moles ratio = table
how can you calculate molecular formula?
using the empirical formula and RFM
what is the word equation for water of crystallisation?
hydrated copper sulphate (blue) > anhydrous copper sulphate (white) + water vapour • calculate mass of water lost • draw a mass, RFM, moles, ratio table
what is it called when there isn’t enough of a substance?
limiting
what is it called when there is more than enough of a substance?
excess
moles should always be the…
same
what’s the equation for percentage yield?
% yield = experimental / theoretical x 100
what is the experimental figure from? percentage yield
the experiment
where is the theoretical figure from? percentage yield
from calculation