Comments | chemistryhelp: 10% solution

sarah1234567891 in chemistryhelp

10% solution

Jun 29, 2011 21:29

HI ( Read more... )

Comments 6

surrey_sucks June 30 2011, 04:41:39 UTC

I'm not sure if this is right, but here is my instinct:

M1V1 = M2V2

(0.88)(x) = (0.1)(1L)

smokeline June 30 2011, 05:20:02 UTC

Yeah, you need the (M1)(V1)=(M2)(V2)

(.88)(x)=(.10)(whatever you want your final volume to be)

Then you add x amount of the formic acid to (final volume - x) amount of water.

sarah1234567891 June 30 2011, 07:14:41 UTC

Can you explain this to me?

I'm following a procedure and they make a 4.25% H3PO4 in buffer

the recipe they use is:

4.25 mL of H3PO4 ( purity 86% density 1.685) + 100 mL buffer

4.25 / 104.25 is not 4.25%

M1V1 = M2V2 doesnt work here. =(

smokeline June 30 2011, 16:22:55 UTC

I guess it depends on whether the purity is by volume, concentration, or weight. The calculations would be different based on that. (And also whether the 4.25% solution is 4.25% by volume, concentration, or weight.)

grenjelybean June 30 2011, 20:01:43 UTC

Volume percent is defined as volume of solute over volume of solvent. so 4.25mL/100mL is 4.25%. But then it's not really because it's not 100% pure H3PO4. So, I don't know.

Concentration can be quite tricky sometimes if you miss exactly how it's being expressed.

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