hi i have been given some questions as homework and i am a bit stuck. if someone could help me with the first one i might understand it more.
given that the molecular weight of methylene blue is 374 what weight was dissolved in 1 litre of water to give a solution of 30 micro mol/litre?
if anyone could help i would greatly appreciate it!!!
maybe im confused, but 30 micromoles of methylene blue isn't it?
NB one micromole is moles i think...
From this formula you can work out the number of mols of solute in the solution, remember that
Now that you have the number of mols you can use the formula
This should give you the weight of the solute, which should be quite a small number, of the order of .
okay all of you are confusing me! i learnt it that moles was avogrado constant which means the amount of particles in a substance as in carbon atoms in exactly 12g of the carbon 12-isotope.
the formula is
n= m/Mr or n=c*v(in cm3)/1000 or c*v(dm3)
finally, n=v(dm3)/24.0 or n=v(cm3)/24000
Thanks for that
(Original post by IChem)
All of what you have said here is true, but mostly irrelevant, you arn't being asked to calculate how many molecules of solvent there are, merely the weight of what has been dissolved. So basically, here is a full solution, because you are getting yourself confused:
Now that you have the number of mols:
Thanks for posting! You just need to create an account in order to submit the post
Already a member?
Oops, something wasn't right
please check the following:
Not got an account?
Sign up now
© Copyright The Student Room 2015 all rights reserved
The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.
Register Number: 04666380 (England and Wales), VAT No. 806 8067 22
Registered Office: International House, Queens Road, Brighton, BN1 3XE