Question

For problems 2 & 3, the density of the sample is 0.9977 g/mL and the molar mass of calcium carbonate is 100.0 g/mol. 2. Calculatethemass(ingrams)ofcalciumcarbonatepresentina50.00mLsampleof an aqueous calcium carbonate standard, assuming the standard is known to have a hardness of 75.0 ppm (hardness due to CaCO3).

Answer 1

1) Use of density formula to calculate mass of sample, M

D = M / V => M = D* V = 0.9977 g / mL * 50.00 mL = 49.885 g of sample

Realize that the sample is the solution.

2) Use ppm concentration to calculate mass of solute (calcium carbonate)

By definition, 75.0 ppm = 75.0 g of calcium carbonate / 1,000,000 g of solution.

You use that ratio to calculate the mass of calcium carbonate in 49.885 g of solution.

Mass of solute = 49.885 g of solution * [75.0 g of calcium carbonate] / [1,000,000 g of solution] =

Mass of solute =  0.00374 g of calcium carbonate

Answer: 0.00374 g of calcium carbonate