## Practise with these MCQs

### Calculating a dilution:

**Exercise 1**: from a commercial solution of ammonia

Calculate the volume of commercial solution needed to prepare a 100 mL solution of NH_{4}OH à 4 x 10^{-3} mol/L.

The information available on the label is as follows::

- For the density, take the smallest value
- For the mass content, take 0.28
- Reminder: M
_{N} : 14 g/mol ; M_{O} : 16 g/mol ; M_{H} : 1 g/mol

### Calculating a mass to be weighed:

**Exercise 2**: mass concentration

Calculate **the mass of ammonium vanadate salt (NH**_{4}VO_{3}) needed to prepare a 100 mL solution of **NH**_{4}^{+} at 100 mg/l.

The information available on the label is as follows:

- M
_{NH4} : 18.0 g/mol
- M
_{salt} : 116.98 g/mol

**Exercise 3**: molar concentration

Calculate the

**mass of barium acetate salt** needed to prepare a 100 mL solution of Barium at

**3 x 10**^{-2} mol/L.

The information available on the label is as follows: