Ibuprofen is an anti-inflammatory drug that is used to treat pain, fever, and inflammation. It's molecular formula is C13H18O2. What is the mass percent of C in ibuprofen?单项选择题
A
76.9%
B
69.9%
C
8.80%
D
15.5%
E
75.7%

Question

Ibuprofen is an anti-inflammatory drug that is used to treat pain, fever, and inflammation. It's molecular formula is C13H18O2. What is the mass percent of C in ibuprofen?

BlackTom AI · Accepted Answer

Question: Ibuprofen is an anti-inflammatory drug that is used to treat pain, fever, and inflammation. It's molecular formula is C13H18O2. What is the mass percent of C in ibuprofen?

Options: ["76.9%", "69.9%", "8.80%", "15.5%", "75.7%"]

First, gather the data needed for a mass percent calculation: carbon atoms = 13, hydrogen atoms = 18, oxygen atoms = 2. Atomic masses approximated as C = 12.01 g/mol, H = 1.008 g/mol, O = 16.00 g/mol.

Next, compute the molar mass contributed by carbon: 13 × 12.01 ≈ 156.13 g/mol. This is the total carbon mass in one mole of ibuprofen.

Then, compute the full molar mass of ibuprofen: carbon 156.13 g/mol + hydrogen 18 × 1.008 ≈ 18.14 g/mol + oxygen 2 × 16.00 = 32.00 g/mol. Sum ≈ 156.13 + 18.14 + 32.00 ≈ 206.27 g/mol.

Now, determine the mass percent of carbon: (carbon mass / total molar mass) × 100 = (156.13 / 206.27) × 100 ≈ 75.66%, which rounds to about 75.7%.

Analysis of each option:

Option 1: 76.9%. This value is close but slightly higher than the calculated 75.7%. The discrepancy could stem from using slightly different atomic masses or rounding at intermediate steps, but it overestimates carbon content by about 1.2 percentage points.

Option 2: 69.9%. This is notably lower than the calculated value. The error here would come from underestimating carbon's share, perhaps by using a smaller carbon mass or a larger total molar mass, which would not align with the actual composition.

Option 3: 8.80%. This is far from the correct carbon mass fraction and seems to reflect confusion between percentages of different elements or a miscalculation of carbon contribution entirely. It ignores the substantial carbon content in an organic molecule like ibuprofen.

Option 4: 15.5%. This value is also far too small for carbon in an organic molecule with multiple carbon atoms; it might correspond to a misapplied ratio or forgetting to include all carbon mass in the numerator.

Option 5: 75.7%. This matches the mass percent calculated from the given molecular formula and standard atomic masses, yielding the carbon fraction around three quarters of the molar mass. The calculation aligns with standard percent-by-mass methodology for a chemical formula.

In summary, the correct approach is to calculate carbon mass from the number of carbon atoms and divide by the total molar mass, then convert to a percentage. The option that mirrors this result, approximately 75.7%, is the one consistent with the standard calculation.

Ibuprofen is an anti-inflammatory drug that is used to treat pain, fever, and inflammation. It's molecular formula is C13H18O2. What is the mass percent of C in ibuprofen?单项选择题

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