1. Topic 8
Acids and Alkalis

2. Starter What is the formula of iron (III) oxide?
What is the formula of carbon dioxide?
What is the formula of calcium oxide?
What is the formula mass of water?
What is the formula mass of methane?

3. Calculating Concentration of a Solution
The concentration of a solution is the quantity of solute dissolved in a certain volume of solution.
The concentration is measured in units of moles per litre (mol/l or mol-1)

4. The following triangle will help you with these calculations:
n = number of moles c = concentration (mol/l) V = volume (litres) n c V
Knowing any 2 of these factors allows you to calculate the third unknown:
n = c x V c= n V = n
V c

5. Example 1
Q. Calculate the number of moles in 500cm3 of a 0.2 mol/l solution.
Volume (V) is 500cm3 = 0.5 litres
Concentration (c) = 0.2 mol/l
n = V x c = 0.5 x 0.2 = 0.1 moles n c V

6. Example 2
Q. A 250ml solution contains 0.5 moles. What is the concentration?
V = 250ml = 0.25l
n = 0.5
c = n / v= 0.5 / 0.25 = 2.0 mol/l n c V