How to calculate the volume required to make a 20 millimolar solution.?
Answer:
0.0023 gm=4.39 X10^-6 moles.
that quantity would =volume times molarity required
4.39times 10^-6=vol(litres)times 20X 10^ -3
=V times 2^10^-2
V(litres) =(4.39times 10-6)/(2times 10^-2)
=(4.39/2) times10^(-6-(-2))
=2.195 times10^-4 litres
=about 2.2 times 10^ -1 mls.
=2.195 times 100 microlitres
219.5 microlitres.
If I've got this wrong I'm sure I will soon get the horse laugh. Good Luck,But check my sums.
1. First figure out how many moles you have of the substance. i.e.
.0023/523.985=?
2. Since 20 millimolar = 2*10^-2 moles, use the molarity formula
Molarity= moles/litre.
Molarity = 2*10^-2
Moles = (what ever the answer you got from 1)
3. Solve for Liters.
First calculate amount in moles:
'moles' = mass/molar mass
concentration = 20 millimolar (i.e. 0.02 moles per litre)
volume (in litres) = 'moles'/concentration
Change volume from litres to millilitres (multiply by 1000).
With your examples the answer is volume = 0.22 ml
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