1
Q
What is empirical formula?
A
Simple ratio in witch atoms combine
2
Q
What is molecular formula?
A
Actual numbers in which atoms combine (actual ratio)
3
Q
Finding empirical formula by experiment (5 steps) e.g. Mg and O
A
- Weigh empty crucible with lid = 20g
- Place Mg ribbon in crucible, close and weight =22.4g
- Heat crucible, open lid periodically (to allow O in)
- Cool crucible to rtp
- Weight crucible = 24g (O has been added)
4
Q
Find empirical formula e.g. MgO
A
Elements - Mg O
Masses- 2.4g + 1.6g
Ar- 24 + 16
Moles- 0.1 + 0.1
Ratios- 1:1
Empirical formula- MgO
5
Q
Finding molecular formula (4 steps)
A
- Find Mr
- Find empirical formula by experiment
- Find empirical mass
- Calculate using empirical formula and Ar
6
Q
formula for n
A
Mr
_________________ =n
Empirical masses
7
Q
chemical formula formula
A
n x empirical formula = chemical formula
