[Tipsy]

A CaCl2 solution has a concentration of 10mg/litre. Express the solutions [CA+2] in PPM

x mg = 40.078/110.98 * 10 mg

x = 3.61 mg

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I got this from my lecturer today as how to calculate the PPM.

wt Ca2+/mwt CaCl2  X  x 10ppm  < - i have copied and pasted that so no typos on my part!

I don't understand why she has put 10ppm where we have 10mg. Is it because ppm=mg/l

I sure hope this is right now! For your sanity and mine  

my final answer would be (assuming my understanding of ppm=mg/l is correct)

3.61 PPM.

and just for curiosity sake, if PPM = mg/l why not just express the answer as 3.61 mg/l . Why have another unit type which means the same?

[Tipsy]

enahs , I guess then that is what my lecturer sent me.

Thankyou.

I am glad i did it the other way though because I think I made every mistake possible and since I only seem to learn from mistakes, then I shouldn't make the same ones again!

I keep hearing voices in my head saying "units, units, units, I must always check my units" 

[Tipsy]

I just printed the posts off ( 6 pages  ) and re-read it all and realised why I didn't get some of it.

I was trying to calculate PPM of Ca instead of focusing on calculating the concentration of Ca expressed in PPM as per the question. Now I understand that I should have thought "concentration" (as well as units!!) it all makes sense. 

Thanks so much, ever grateful...I am off to do the next 15 questions...so don't run away just yet