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Old Aug 28th 2016, 04:30 PM   #1
mz243100
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Need help with Enviromental Chemistry Problem

Hello

I have a question on my assignment that goes like this:
A water sample has a pH of 8.21 and a total Ca2+ concentration of 143 ppm.(3 marks)

What are the molar concentrations of CO32− and HCO3−?
What is the total alkalinity of the water?

I know that the total alkalinity= 2[CO32-) + [HCO3-]+ [OH-] - [H+]
the concentrations of OH- and H+ are obvious from the pH
I know that I can relate the [CO32-] to [HCO3-] through the expression:
CO32- + H+ -------> HCO3-
What is confusing me is how to derive the HCO3- and CO32- from the get go, also what can we derie from the Ca2+ concentration? I am confused on how to arrive to the concentration of CO32- and HCO3- using the Ca2+ concentration.

Any help is much appreciated
Thanks
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