Serial Dilutions

Royality

Royality

Royality

Soldato
Joined
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Can anyone help me with some serial dilutions at all? I just can't get my head round them... :(

So I start with a 1mol solution of Copper Sulphate and want to get the measurements of 0.5,0.4,0.3,0.2,0.1 and 0.0mol solutions by adding distilled water. I also want the simplest ratios producing the smallest amount of Copper Sulphate overall.

i.e: Ratio of 5:5 makes 0.5mol CuS04, overall 10cm3.

I hope you get me, can someone plllease help me. I really need help with this. :(

Cheers. :)
 
I'm not sure i totally get what your talking about but:

if you have a 1 molar solution of copper sulphate you have one mole of copper sulphate in one litre of water.

its then just simple ratios to dilute it. eg for a 0.5 molar solution you simply take equal volumes of water and the 1molar copper sulphate.

for a 0.4 molar solution, you want 4 parts copper sulphate and six parts water. So for 10ml of 0.4 molar solution you take 4ml of your 1 molar copper sulphate and add 6ml of water to it.

if you wanted 1ml it would be 0.4ml copper sulphate and 0.6ml water. The volume isn't the important part, its the ratio of the copper sulphate and the water which dictates its concentration for a given volume.


thats probably just confused you more, but i've spent all day in lab, and i'm not thinking that straight.
 
Sorry, I didn't explain it clearly. :rolleyes:

What I mean is how to get 0.4mols /dm3 from 0.5mols /dm3, 0.3 from 0.4, 0.2 from 0.3 and etc. :)
 
right, i'm absolutely useless at explaining this, always have been, I understand it, but i can just never explain it to anyone but i'll give it a go:

0.4 mol dm3 from 0.5 mol dm3

you want something that is 80% of the strength of the 0.5 mol dm3 solution you already have.

so if you start with 100ml of 0.5 mol dm3 you have effectively 50ml of 1 molar copper sulphate and 50ml water. So to dilute to 0.4 molar, you take 80ml of the 0.5 molar and add 20ml water.

so you now have 100ml made up of 80ml of the 0.5molar (effectively 40ml of 1 molar copper sulphate) and 20ml water, so in total you have 40ml of 1 molar copper sulphate and 60ml water, or a 0.4 molar solution.


then just repeat for the lower concentrations, if that makes any sense at all, apologies if it doesn't.
 
Aaaaaarg I still can't do it. :(

I'm being really rude here but could you write down the ratios for me?

I understand the ratio for 0.5 to 0.4 in 8 parts 0.5 and 2 parts water right? :confused:
 
I can send you a sheet from my pharmacology workbook which we used when making serial dilutions of salicylate. I'll email it in one hour (apprentice is on), it's actually VERY easy... once you understand it, of course.

quick example, if you have 10ml of a 1mM solution, you take 1ml of solution and add 9ml distilled water. You now have 10ml 0.1mM. If you want to go from 0.5mM to 0.4mM, it's a bit more complicated but I'll cover it for you later if the above post wasn't enough (editing so can't see the posters name ;))
 
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Sorry to be persistent but I couldn't send you a message Mikol, you should be able to see my e-mail, can you send me that stuff? :) Cheers.
 
Copper sulphate (ml) Water (ml) Molarity
100 0 0.5
80 20 0.4
75 25 0.3
66.6 33.3 0.2
33.3 66.6 0.1
0 100 0.0

thats starting with 100ml of 0.5 molar solution, and sucessively diluting it.

those figures are just off the top of the head(so they may well be wrong!), so you'd do well to check them. This sort of thing should be in any decent gcse or alevel chemistry text book, possibly even on wikipedia.

formatting has screwed that 'table' i put in
 
just to clarify, the figures i've given:

the first figure in each line is the amount of the previous solution you need to take, the second figure is then the amount of water needed to top it up.
 
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