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)

360.1

Answer 2

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