1.3.3, 1.4 Empirical/Molecular; Water of Crystallisation

Empirical formula
> s__ p__ f__ w/ a w__ no. r__ of atoms

simplest possible formula, whole, ratio

Molecular formula
> a__ no. & t__ of each a__ in a molecule

actual, type, atom

Finding molecular formula from empirical
e.g. if empirical is CH₂ , molar mass of compound is 98g/mol
> Mol. formula is (CH₂)_n
> n = __ M_r / __ M_r

molecular, empirical

Anhydrous: s__ w/ __ w__ o_ __

substance, no water of crystallisation

Hydrated: s__ c__ chemically w/ w__ & has d__ no. of w__ m__ in their s__

substance combines, water, definite, water molecules, structure

Water of crystallisation: s__ no. of m__ of w__ associated w/ a c__ s__

specific, moles, water, crystal structure

n =

m/M

1mol of Oxygen (O2) has how many atoms
a) 6.02 × 10²³
b) 2 × 6.02 × 10²³

b

1mol of Oxygen (O2) has how many molecules
a) 6.02 × 10²³
b) 2 × 6.02 × 10²³

a

C = (w/ volume)

n/V

% yield = a__ yield / t__ yield x 100

actual, theoretical

Finding excess & limiting reagents
e.g. if 0.40mol of Na reacts w/ 0.25mol of S → Na₂S
1. Write balanced equation: 2Na + S → Na₂S
2. Ratio is _:1 , thus 0.40mol of Na needs 0.20mol of S (40/2 bc of ratio)
3. There is 0.25mol of S thus it is in __
> Thus __ is the l__ reagent

2, excess, Na, limiting

1 mole of any gas occupies __dm³ at RTP
THUS at RTP, V = __

24, 24n

1 mole of any gas occupies __dm³ at STP (0C, 1atm)
THUS at STP, V = __

22.4, 22.4n

Standard solution: one that’s c__ is a__ known

conc, accurately