How to prepare solutions and dilutions

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 NH₄OH 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 (NH₄VO₃) needed to prepare a 100 mL solution of NH₄⁺ 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:

• M_Ba : 137.3 g/mol