Units of Concentration

[Davoo!]

Hello everyone!

Yr 12 Chem this year and flunking BAD.
Anyways, units of concentration is buggering me pretty badly. Anyone willing how to show me how to convert from one unit to another? As in all of them literally? Yeah I know what your thinking. I know I suck haha.

Thanks dudes and dudettes!

[chem-nerd]

Check out Mao's "Confusing Chemistry Concentrations" in the notes section

[stonecold]

All I really know is how to get to ppm, first you get it to grams per litre, then multiply by 1000, and you have ppm.

[naved_s9994]

All I really know is how to get to ppm, first you get it to grams per litre, then multiply by 1000, and you have ppm.

Well thats because its 10^6
And ppb is 10^9

[m@tty]

g/L is 1/1000 or parts per thousand(10^3), so clearly to achieve parts per million(10^6) it is necessary to multiply by 1000
i.e. 1 g/L = 1000 ppm

I've forgotten why I typed this post

[Martoman]

I like to think of it as a fraction. ppm means that we want to get 10^6 in the denominator and the numerator is what we put down as our answer.

Eg: 1/10^6 = 1 part per million, the per means that there is 1 in the numerator and 10^6 in the dominator.

Eg: 40 / 2*10^6 means that we must multiply the top and bottom by 1/2 so that the two disappears in the bottom and then it becomes 20/10^6 so you know its 20 parts per million.

People say just multiply by 1000 because what that is effectively doing is multiplying the TOP numerator AND denominator by 1000. So really, you aren't changing anything, you are multiplying through by 1000/1000, which is 1. When you multiply by 1, you get? same answer right? (hopefully). This is a common misconception, that works, but not many people understand why it works. This is the maths behind it.

[physics]

i only know how to convert from mol l^-1 to g L^-1
from one to the other u multiply the mol^-1 by the molar mass and then u get g^-1

hope this is right!
dw i suck in chem too

[Edmund]

i only know how to convert from mol l^-1 to g L^-1
from one to the other u multiply the mol^-1 by the molar mass and then u get g^-1

hope this is right!
dw i suck in chem too

Yeah you just convert mols to grams

[Martoman]

Realise that these conversion from to can only happen because the molar mass is defined as

What you are effectively doing is "dimensional analysis" which is basically crossing off commons in the numerator and denominator. This process is:



The moles cancel out and WOW! You have !!!!

A similar process is observed when going the other way.