moles 4.4 Flashcards
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
