chemistry

A student needs 25 cm3 of 0.1 mol dm-3 of ethanoic acid for an experiment. They are given a bottle of ethanoic acid with a concentration of 1 mol dm-3. Calculate the volume of the ethanoic acid needed from the bottle and the volume of water to be added so as to get the correct volume and concentration for their experiment

Reply 1

hmkh026

First calculate the number of moles needed: 25/1000 x 0.1 = 0.0025mol
Then calculate the volume from the bottle needed to attain this number of moles: 0.0025/1 so 0.0025dm3 (2.5cm3)
Then calculate vol8ume of water needed: 25-2.5=22.5cm^3

Reply 2

TypicalNerd

Original post by hmkh026

This is a perfectly correct approach to doing this. For future reference, though, it may marginally simpler to use the dilution equation:

Undiluted concentration x Undiluted volume = Diluted concentration x Diluted volume

Which rearranges to:

Undiluted volume = (Diluted concentration x Diluted volume)/(Undiluted concentration)

Where the diluted volume is the volume of solution you want to prepare in this case (so 25 cm^3) and the undiluted volume is the amount of the original solution needed.
You then work out the volume of water added using

Water added = Diluted volume - Undiluted volume