Question

1. a 0.244 g sample of calcium carbonate, caco₃, was recovered from a sample of hard water. how many formula units of caco₃ were in the sample?

Explanation:

Step1: Find molar mass of CaCO₃

The molar mass of CaCO₃ is $40 + 12+3\times16=100$ g/mol.

Step2: Calculate moles

Moles = $\frac{mass}{molar - mass}=\frac{0.244}{100}=0.00244$ mol. Since 1 mole of CaCO₃ is 1 formula - unit, there are 0.00244 formula - units.

Answer:

0.00244 formula - units