Question

Cortisone is a molecular substance that has $21$ 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 $360.1$

Let the molar mass of Cortisone be x.

Given that it contains 21 carbon atom and the mass percentage of carbon in cortisone is 69.98%.

So, $\frac{12\times 21}{x}\times 100=69.98$
$\Rightarrow x=\frac{12\times 21\times 100}{69.98}=360.10$