1.6 The Mole

Question 1

How to calculate gram formula mass.

Answer 1

The gram formula mass of a substance is the mass of one mole of that
substance.

The relative atomic masses of selected elements are listed in your data
booklet. These can be used to calculate the gram formula mass of a
substance.

Eg:

Find the GFM of Potassium Oxide (K2O)

firstly find the RAM of Potassium and Oxygen on page 7 of your data booklet.

The RAM of potassium is 39 and the RAM of oxygen is 16.

For each mole of the element that you have multiply it with the RAM.

K2 = 39 x 2=78
O = 16 x 1=16

After this, add them together making the GFM of potassium oxide.

78 + 16 = 94g.

Question 2

How do you calculate the mass of a compound?

Answer 2

M = N x GFM

Question 3

How do you calculate the number of moles if you have the mass and gfm?

Answer 3

N = M
__
GFM

Question 4

How do you calculate the formula mass if you have the mass and the number of moles?

Answer 4

GFM =. M
___
N

Question 5

How do you calculate the number of moles if you have the concentration and volume?

Answer 5

N = C x V

Question 6

How do you calculate the concentration in mol l-1 ?

Answer 6

C =. N
___
V

Question 7

Balance this compound:

Ca + O2 ————> CaO

Answer 7

2Ca + O2 ————> 2CaO