Australia's Science Forum

Hi everyone,
Can someone work out for me what molarity a 5% solution of zinc sulfate is please?
I am not sure how you convert from one to the other.
Thanks,
Helen

Just wondering why you would need to convert. Unfortunately I don't know, but if I'm asked for a 5% solution I just give it to them and mark it as such. It would be approx 0.2M for purposes of knowing how to colour code it. Hope this helps.

Hi Dime,
I have a 5% solution made up. The teacher wants a .1M solution and I have run out of solid.
I told her it was about 1.6 just working it out in my head but she wanted an exact figure and I am not sure how to do this.
Helen

Percentage sol. 1g solid per. 100ml. of water

You need 28.8g made up to a litre to make 0.1M, therefore 2.88g to make 0.1M/100mls you have approx twice this so roughly 0.2M or 0.174M to be exact (5g devided by 2.88g) I think thats right! MariaC

Hi Helen
Don't know if this will help but I have this formula for percent to molar solutions

required molarity x molecular weight x volume required (in mL)
mL of stock solution required = ________________________________________________________
stock percentage x 10

Once you have the amount of stock required you make up to 1L. Hope that helps
Krysia

Hi Again
that post didn't come out quite like it should. What it is in long hand is that the amount of stock solution required ( here your 5% solution)is equal to the required molarity x molecular weight x volume required divided by the stock percantage x 10. Or for a 0.1M you need 0.1 x 287.54 x1000 =28754 divided by 50 =575.08mL Then make up to 1L.
Krysia

Thanks,
I knew someone would be smart enough to work it out for me!!
Helen

HI
There is a good website that has a calculator for working out lots of different solution probs like percent to molar solution or molar to molar etc. If you'd like to try it out the address is
www.cleanroom.byu.edu/MolestoAnything.phtml
Just for future reference if you ever need it.
Krysia