How to prepare solutions and dilutions

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 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: MN : 14 g/mol ; MO : 16 g/mol ; MH : 1 g/mol

Exercise 1


The volume required is:


6 mL
126 µL
27 µL
2.5 mL
Correction
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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:

  • MNH4 : 18.0 g/mol
  • Msalt : 116.98 g/mol

Exercise 2


The mass to be weighed is:


260 mg
121 mg
13 mg
65 mg
Correction
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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:
  • MBa : 137.3 g/mol

Exercise 3


The mass to be weighed is:


1.3 g
321 mg
766 mg
126 mg
Correction
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