Question

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

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

Answer 1

Answer: (D)

In cortisone
$69.98gC\equiv 100g$ cortison
$1$ mole of cortisone contains $21$ moles of carbon atoms or $252g$ of carbon
$252g$ carbon $\equiv$ 1 mol cortisone
$69.98g$ carbon $\frac{=}{69.98}252$ mol cortisone
$\frac{69.98}{252}$ mol cortisone $\equiv 100g$
1mol cortisone $=\frac{100g\times 252}{69.98}=360.10g$
$\therefore$ Molar mass of cortisone $=360.10gmo{l}^{-1}$