Question

Cortisone is a molecular substance containing 21 atoms of carbon per molecule.The weight percentage of carbon in cortisone is 69.98%.What is the molecular weight of cortisone ?

Answer 1

The weight of 21 carbon atom = 12 g/mol x 21 = 252 g/mol
​Let the molecular weight of cortisone is Y
Y $\times$69.98/100 = ​252 g/mol
Y = 252g/mol​ x 100/69.98 = 25200/69.98 g/mol = 360.10 g/mol
Molecular weight of cortisone = ​360.10 g/mol