Summary Grade 12 IEB Physical Sciences - Quantitative Chemistry Notes (Chemistry Section A)

The Mole Concept

The technique of being able to quantitatively measure the amount of substance present in a
chemical system.
Using the number of moles present to calculate:
- mass of substance present
- volume of substance present (gases only)
- number of particles of substance present

Mole
= SI unit for amount of substance

Molar mass
= the mass in grams of one mole of that substance.

Molar volume
= the volume that one mole of any gas will occupy at STP.

KEY
n = mole (mol)
m = mass (g)
M = molar mass (g.mol-1)
V = volume (dm3 = cm)
Vm = molar volume = 22.4 dm3.mol-1 at STP
N = number pf particles
NA = 6.02 x 1023 mol-1

Formulae:

𝑚
n=
𝑀

𝑣
n=
𝑉𝑚

𝑁
n=
𝑁𝐴

, Concentration
= the amount of solute per unit volume of solution (mol.dm-3)

𝑛
c=
𝑉

𝑚
c=
𝑀𝑉




Solute: the substance that is dissolved in the solvent in the solution.

Solvent: the substance in which another substance is dissolved into, forming a solution.

Solution: a homogeneous mixture of solute and solvent. n = mole (mol)



NOTE: Concentration of a diluted solution

C1 x V1 = C2 x V2