**Calculating Calcium Hardness as CaCO3**

The hardness (in mg/L as CaCO3) for any given metallic ion is calculated using Equation

Calcium hardness (m/L) as CaCO3/equivalent weight of CaCO3

**=** Calcium (mg/L)/equivalent weight of calcium

Example:-

A water sample has calcium content of 51 mg/L. What is this calcium hardness expressed as CaCO3?

Solution

Referring to Equation:

x mg/L /50.045=51 mg/L /20.04

x=51 x 50.045/20.04

=127.36 mg /L Ca as CaCO3

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50.045 means

Equivalent weight of Calcium Carbonate

equivalent weight of CaCO3 (100/2). CaCO3 is Ca++ and CO3–. Equivalency means weight per ions.

Frank R. Spellman and it states that the answer is 124.8 mg/L Ca as CaCO3.

Seems to follow the calculation I always knew of 2.5(Ca++) thus 2.5*51=127.5 mg/L

Close enough…….

Who’s right and who’s wrong?

thanks your clarification 124.8 is accuracy fig

Molar mass (CO3(2-)) = M(C) + 3 x M(O) = 12+ 3 x 16 = 60 g/mole. Molar mass (CaCO3) = M(Ca) + M(C) + 3 x M(O) = 40 + 12 + 3 x 16 = 100 g/mole. Divide the molar mass by the ion charge or oxidation number (for CaCO3) to determine equivalent (Eq.) weights. Eq. weight (HCO3(-)) = 61 / 1 (charge) = 61 g/Eq.

So eq wt of Caco3 is 61g/eq it is ok

Pls can u apply this conversion to to any sample of interest esp soil sample. Hw many unit do you av to subtract to obtain an accurate accuracy figure?.. reply ASAP pls

And pls whr did u derive 20.04? Pls I need a clearification

Is it ca3-ca?

Calculation above is wrong.

If x=51 x 50.045/20.04,

then x=127.36 mg /L Ca as CaCO3

not x= 124.8!

Thanks to point us, we updated