Question

Cortisone is a molecular substance containing $21$ atoms of carbon per molecule. The mass percentage of carbon in cortisone is $69.98$%. Its molar mass is:

• A. $176.5$
• B. $252.2$
• C. $287.6$
• D. $360.1$

Answer 1

The correct option is D $360.1$

Cortisone is a molecular substance containing $21$ atoms of carbon per molecule.
$1$ mole of cortisone contains $21\times 12=252$ g of $C$.
The mass percentage of carbon in cortisone is $69.98$%.
Its molar mass will be $\frac{100}{69.98}\times 252=360.1$ g/mol.