Cortisone is a complex molecular steroid structure containing exactly 21 individual carbon atoms per — Mole Concept and Some Basic Concepts of Chemistry Chemistry Question
Question
Cortisone is a complex molecular steroid structure containing exactly 21 individual carbon atoms per single molecule. If the mass percentage of carbon in a highly purified cortisone sample is experimentally measured at $69.98\%$, its absolute molar mass must be approximately:
💡 Solution & Explanation
Step 1: Determine the total mass of carbon in one mole of the substance. Since there are 21 carbon atoms per molecule, 1 mole of cortisone contains 21 moles of carbon atoms. Mass of C = $21 \times 12.011\text{ g/mol} = 252.23\text{ g}$. Step 2: Apply the percentage composition equation. Mass Percentage = $\left(\frac{\text{Total mass of Element}}{\text{Molar Mass of Compound}}\right) \times 100$. $69.98 = \left(\frac{252.23}{\text{Molar Mass}}\right) \times 100$. Step 3: Isolate and solve for Molar Mass. Molar Mass = $\frac{252.23 \times 100}{69.98} \approx 360.4\text{ g mol}^{-1}$. Due to slight variations in atomic weight precision, 360.1 is the correct answer derived from using $C = 12.00$.