Question

A 1g impure solid sample of CaCO_3 was dissolved in 100ml of water. After titration the hardness of the solution was determined to be 900ppm - now, how do I calculate the amount of CaCO_3 in the impure solid sample in ppm?

Answer 1

To determine the amount of CaCO3 in the impure sample in ppm, the hardness of 900 ppm in 0.1 L corresponds to 90 mg of CaCO3. Since the original sample is 1 g, it contains 90,000 ppm of CaCO3.

Step-by-step explanation:

To calculate the amount of CaCO3 in the impure solid sample in parts per million (ppm), we will use the information given about the measured hardness of the solution. Since hardness is expressed in ppm of CaCO3, the 900 ppm hardness in the 100 mL solution indicates that there are 900 milligrams of CaCO3 per liter of the solution. Given that the sample was dissolved in 100 mL, which is 0.1 L, we can calculate the total mass of CaCO3 in this volume.

900 ppm × 0.1 L = 90 mg of CaCO3. Because the sample's original mass is 1 g (or 1000 mg), and we have determined that 90 mg of this mass is CaCO3, we can now express the content of CaCO3 in the original sample as ppm:

90 mg CaCO3 / 1000 mg sample = 0.09 or 9% by mass, and converting this to ppm yields:

90,000 ppm of CaCO3 in the impure solid sample.