What is the mass percent of carbon in testosterone (C19H28O2)?

• A. 54.2%
• B. 79.1%
• C. 88.6%
• D. 65.3%

Answer: (B)

Verified step by step guidance

1. Identify the molecular formula of testosterone, which is C19H28O2. This tells us the molecule contains 19 carbon atoms, 28 hydrogen atoms, and 2 oxygen atoms.
2. Calculate the molar mass of testosterone by summing the atomic masses of all atoms in the formula. Use the atomic masses: Carbon (C) = 12.01 g/mol, Hydrogen (H) = 1.008 g/mol, Oxygen (O) = 16.00 g/mol. The formula for molar mass is: \(M = (19 \times 12.01) + (28 \times 1.008) + (2 \times 16.00)\).
3. Calculate the total mass of carbon in one mole of testosterone by multiplying the number of carbon atoms by the atomic mass of carbon: \(m_{C} = 19 \times 12.01\) g.
4. Calculate the mass percent of carbon in testosterone using the formula: \(\text{Mass \% C} = \left( \frac{m_{C}}{M} \right) \times 100\%\) where \(m_{C}\) is the total mass of carbon and \(M\) is the molar mass of testosterone.
5. Interpret the result to determine which of the given answer choices matches the calculated mass percent of carbon.