Answer to Question #153704 in General Chemistry for Zoe Buchalter

Question

Medicinal formulations of calcium sometimes come in the form of a liquid.  Calcium phosphate is sometimes delivered by the spoonful (15 mL).  Is it accurate for the drug company to say that one teaspoon of calcium phosphate contains 0.1 g of calcium if there is 1.671 g of calcium phosphate per 100 mL?

Answer 1

the molar mass of calcium phosphate is 310.18 g/mole. Calcium's atomic mass is 40.08, and there are three calciums per molecule of Ca₃(PO₄)₂. The mass percentage of calcium is thus (3*40.08)/(310.18) = 0.3876%.

If we have 1.671g calcium phosphate per 100ml, we'd have (15ml/100ml) or 15% of that in 15ml. That calculates to 0.0972g Ca per 15 ml, which could be rounded to 0.1g .