Preparing a Solution of Known Molarity
Molarity is the number of moles in 1 litre of the SOLUTION.
When you make up a solution of specified molarity, you dissolve the required number of moles in a small volume of the solvent and then make the FINAL VOLUME OF THE SOLUTION UP TO the volume required. You do not know in advance exactly what volume of solvent you will need, you only know the combined volume of the solute and solvent.
To prepare 1000 cm3 of a 1.672 M solution of Dextrose (RMM = 180.0):
Weigh out 300.96 grams of Dextrose
Add a little water to dissolve the Dextrose
Add water to make the final volume UP TO 1000 cm3.
Calculate the MASS of Dextrose needed - you need
1.672 moles of Dextrose therefore:
Mass = Moles x RMM = 1.672 x 180.0 g = 300.96 grams
1.672 moles of Dextrose therefore:
Mass = Moles x RMM = 1.672 x 180.0 g = 300.96 grams
Weigh out 300.96 grams of Dextrose
Add a little water to dissolve the Dextrose
Add water to make the final volume UP TO 1000 cm3.
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