1. Reacting Masses

2. Learning objectives
Know the value of one mole for mass, gas volume and liquid volumes and concentrations
Be able to establish balanced compounds from mol calculations
Evaluate the terms concentrated and dilute for solutions

3. Gases
We know how many atoms are in one mole and we can use that with molar mass, but gases are much harder to measure the mass of so what do we do here?
Luckily all gases take up the same volume when kept in the same conditions

4. Gas volumes
At room temperature an pressure (25˚C and 1atm) the volume of 1 mole is 24dm3
(At “Standard temperature and pressure it is 22.4dm3 )

5. Using this: N2 (g) + 3H2 (g) 2NH3 (g) 1mole + 3 moles 2 moles
24dm3 + (3 x 24dm3) (2 x24dm3)
1 volume + 3 volumes 2 volumes

6. To Work out the concentration
Number of moles(mol) =
Concentration (mol/dm3)x volume (dm3)

7. Hooray, some calculations!
Solute Mass of solute Volume Concentration (g) (dm3) (mol/dm3)
1. LiBr ?
2. NH4Cl ?
3. KOH ?
4. NaCl ?
5. BaCl ?
6. KCl ?
7. NaOH ?
8. CuSO ?
9. Al(NO3) ?
10. (NH4)2SO ?

8. Answers 1. 1 mol/dm3 2. 0.75 mol/dm3 3. 2 mol/dm3 4. 0.1 mol/dm3g g g