Empirical formula + molecular formula

Question 1

What is empirical formula?

Answer 1

Simple ratio in witch atoms combine

Question 2

What is molecular formula?

Answer 2

Actual numbers in which atoms combine (actual ratio)

Question 3

Finding empirical formula by experiment (5 steps) e.g. Mg and O

Answer 3

1. Weigh empty crucible with lid = 20g
2. Place Mg ribbon in crucible, close and weight =22.4g
3. Heat crucible, open lid periodically (to allow O in)
4. Cool crucible to rtp
5. Weight crucible = 24g (O has been added)

Question 4

Find empirical formula e.g. MgO

Answer 4

Elements - Mg O
Masses- 2.4g + 1.6g
Ar- 24 + 16
Moles- 0.1 + 0.1
Ratios- 1:1
Empirical formula- MgO

Question 5

Finding molecular formula (4 steps)

Answer 5

1. Find Mr
2. Find empirical formula by experiment
3. Find empirical mass
4. Calculate using empirical formula and Ar

Question 6

formula for n

Answer 6

Mr
_________________ =n
Empirical masses

Question 7

chemical formula formula

Answer 7

n x empirical formula = chemical formula