6. A chemist needs 457.8 g of KMnO4 to make a solution. How many moles of KMnO4 is that?

7. How many moles of erythromycin (C37H67N013), a widely used antibiotic, are in 1.00 x 10°g of the

substance?

8. Cortisone (C21H2805) is a synthetic steroid that is used as an anti-inflammatory drug. How many moles of

cortisone are present in one 10.0 mg tablet?

6) 2.9 moles of KMnO4

7) 1.36*10^-3 moles

8) 2.8*10^-5 moles

Explanation:

6) Number of moles is given as mass/molar mass

Mass of KMnO4 = 457.8

Molar mass of KMnO4 = 158.034 g/mol

Number of moles of KMnO4 = 457.8 g / 158.034 g/mol = 2.9 moles of KMnO4

7) mass of erythromycin = 1.00*10^0 g

Molar mass of erythromycin = 733.93 g/mol

Number of moles of erthromycin = 1.00*10^0 g / 733.93 g/mol = 1.36*10^-3 moles

8) mass of cortisone = 10.0 mg = 10*10^-3g

Molar mass of cortisone = 360.45 g/mol

Number of moles of cortisone = mass/molar mass = 10*10^-3 g / 360.45 g/mol = 2.8*10^-5 moles