Halitosis Posts: 2, Reputation: 1 New Member #1 Dec 28, 2011, 04:13 PM
If I have mg/L of Hardness (CaCO3) , can I calculate mg/L of Calcium?
I have 100 mg/L of CaCO3, can I calculate mg/L of Calcium? If so, what are the steps?
 Unknown008 Posts: 8,076, Reputation: 723 Uber Member #2 Dec 29, 2011, 02:42 AM
Do you mean calcium ions?

If there are 100 mg of CaCO3 in 1 litre of water, how many moles of CaCO3 are there in the water? Use the relative molecular weight of CaCO3.

When you get this, find the number of moles of Ca ions there would be in the water and multiply that amount of moles by the relative atomic mass of Ca.
 Halitosis Posts: 2, Reputation: 1 New Member #3 Jan 3, 2012, 09:37 AM
Thanks for your reply. Some friends at a chemistry lab sent me this that walks me through each step:

Total hardness is defined as the sum of the calcium and magnesium cation concentrations, expressed as an equivalent weight of calcium carbonate in mg/L:
Total Hardness as CaCO3 = (Ca Hardness as CaCO3) + (Mg Hardness as CaCO3)

Ca Hardness as CaCO3 = (concentration of Ca ion) x [(Molar Mass of CaCO3)/ (Molar Mass of Ca)]

(Molar Mass of CaCO3)/ (Molar Mass of Ca) = (40.08 + 12.011 + (3x16)) / (40.08) = 2.497

Therefore,
Ca Hardness as CaCO3 = (concentration of Ca ion) x (2.497)
or
concentration of Ca ion = (Ca Hardness as CaCO3) / 2.497

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