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Calculate potassium permanganate solution required to prepare 100ml of solution of which 1 part dilute with 7 parts of water mixed with 1 in 8000 solution .

Reply 1

TypicalNerd

Original post

by KPharm1

Calculate potassium permanganate solution required to prepare 100ml of solution of which 1 part dilute with 7 parts of water mixed with 1 in 8000 solution .

1 in 8000 solution is 100% x 1/8000 = 0.0125% (w/v), which is to say that for every 100 mL of solution you have, 0.0125 g of KMnO4 is dissolved in it. This must therefore be the mass of KMnO4 in the solution since the volume is conveniently 100 mL.

That being said, they’ve told you that the original KMnO4 solution was diluted with 7 parts of water (i.e there was 1 part of undiluted KMnO4 solution). How many “parts” are there in total and given that the total volume of this number of parts is 100 mL, what must the volume of the undiluted KMnO4 solution be?

Lastly, how might you use the mass of KMnO4 (0.0125 g) and the volume calculated above to work out the concentration of undiluted KMnO4?

Reply 2

TypicalNerd

Original post

by TypicalNerd

1 in 8000 solution is 100% x 1/8000 = 0.0125% (w/v), which is to say that for every 100 mL of solution you have, 0.0125 g of KMnO4 is dissolved in it. This must therefore be the mass of KMnO4 in the solution since the volume is conveniently 100 mL.
That being said, they’ve told you that the original KMnO4 solution was diluted with 7 parts of water (i.e there was 1 part of undiluted KMnO4 solution). How many “parts” are there in total and given that the total volume of this number of parts is 100 mL, what must the volume of the undiluted KMnO4 solution be?
Lastly, how might you use the mass of KMnO4 (0.0125 g) and the volume calculated above to work out the concentration of undiluted KMnO4?

I’ve just realised that I missed an easier way of doing this problem (which is a valid method rather than by coincidence- this is more apparent if you have come across the dilution equation m1V1 = m2V2)

If the first method doesn’t help or you want less work, start by calculating the number of parts the diluted (1 in 8000) solution is made up of. Then multiply the concentration of the solution by the number of parts. This will give the undiluted concentration.