Cortisone is a molecular steroid substance containing exactly 21 atoms of carbon per single molecule — Mole Concept and Some Basic Concepts of Chemistry Chemistry Question
Question
Cortisone is a molecular steroid substance containing exactly 21 atoms of carbon per single molecule. If the mass percentage of carbon in cortisone is experimentally determined to be $69.98\%$, its molar mass is approximately:
💡 Solution & Explanation
Step 1: Find the total mass of Carbon in one mole of cortisone. Since there are 21 Carbon atoms per molecule, $1\text{ mole}$ contains 21 moles of C atoms. Mass of C $= 21 \times 12.011\text{ g/mol} = 252.23\text{ g}$. Step 2: Use the percentage composition formula. $\text{Mass \%} = \frac{\text{Mass of element}}{\text{Molar mass of compound}} \times 100$. $69.98 = \frac{252.23}{M} \times 100$. Step 3: Solve for Molar Mass ($M$). $M = \frac{252.23 \times 100}{69.98} \approx 360.4$ (closest to 360.1 depending on exact C atomic weight used).