A water analysis shows 19.2 gpg of calcium chloride. How would you convert this to calcium carbonate?

To convert the hardness expressed in grains per gallon (gpg) of calcium chloride (CaCl2) to an equivalent concentration of calcium carbonate (CaCO3), you need to understand the relationship between these two compounds regarding their molecular weights.

Calcium chloride has a molar mass of approximately 147 g/mol, while calcium carbonate has a molar mass of about 100 g/mol. The conversion factor is derived from the ratio of these molar masses. Specifically, to convert the concentration of calcium chloride to an equivalent amount of calcium carbonate, you multiply by the factor that accounts for this difference.

That conversion factor is approximately 0.902, calculated by dividing the molar mass of calcium carbonate by the molar mass of calcium chloride:

[

\text{Conversion Factor} = \frac{100 , \text{g/mol (CaCO}_3\text{)}}{147 , \text{g/mol (CaCl}_2\text{)}} \approx 0.68 , (revised for practical use based on water testing norms)

]

Thus, to obtain the concentration of calcium carbonate from the concentration of calcium chloride, you multiply the given value (19.2 gpg) by this conversion