## 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/lThe 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/LThe information available on the label is as follows:

- M
_{Ba}: 137.3 g/mol