Question

Calculate the mass (in grams) of calcium carbonate present in a 50.00 mL sample of an aqueous calcium carbonate standard, assuming the standard is known to have a hardness of 75.0 ppm (hardness due to CaCO3).

Answer 1

In one gram of standard, there are 75 × 10⁻⁶ grams of CaCO3
Thus, in 50 ml, there are 50 grams of standard (assuming density of standard equal to that of water) so grams of CaCO3 are:
50 × 75 × 10⁻⁶
= 3.75 × 10⁻³ grams