Section 2: Calculating the Number of Moles
If you know the molarity of a component and the volume of solution involved, you can calculate the number of moles of the component.
How many millimoles of Dextrose are there in 60 ml of a 0.7536 M solution of Dextrose? Answer to 5 significant figures.
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There are 45.216 millimoles of Dextrose to 5 significant figures.
Number of Moles = Molarity x Volume of Total System (in dm3 )
60 ml = 0.06 dm3
Thus: Number of Moles of Dextrose present = 0.7536 x 0.06 moles
Number of Moles of Dextrose present = 0.045216 moles
Millimoles of Dextrose = 1000 x 0.045216
Millimoles of Dextrose = 45.2160 = 45.216 millimoles to 5 significant figures.
Molarity = Number of Moles
Volume of Total System (in dm3 )
which rearranges to:Volume of Total System (in dm3 )
Number of Moles = Molarity x Volume of Total System (in dm3 )
60 ml = 0.06 dm3
Thus: Number of Moles of Dextrose present = 0.7536 x 0.06 moles
Number of Moles of Dextrose present = 0.045216 moles
Millimoles of Dextrose = 1000 x 0.045216
Millimoles of Dextrose = 45.2160 = 45.216 millimoles to 5 significant figures.
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