What is the molecular weight of ibuprofen, $\mathrm{C}_{13} \mathrm{H}_{18} \mathrm{O}_{2}$ ? Note: Chemists like to distinguish between whether the polyatomic structure is held together exclusively by covalent bonds or a mix of covalent and ionic bonds. For the example of ibuprofen, all the bonds holding the polyatomic complex together are covalent. So, Chemists use the name "molecular weight" instead of "formula weight". Both words have the same meaning, otherwise. a) $29.0 \mathrm{amu}$ b) $206.3 \mathrm{amu}$ c) $289.4 \mathrm{amu}$ d) $377.7 \mathrm{amu}$ d) b) c) a)

Step 1 ：To find the molecular weight of a compound, we need to add up the atomic weights of all the atoms in the compound. The atomic weights of Carbon (C), Hydrogen (H), and Oxygen (O) are approximately 12.01 amu, 1.008 amu, and 16.00 amu respectively.

Step 2 ：So, the molecular weight of ibuprofen, \(\mathrm{C}_{13} \mathrm{H}_{18} \mathrm{O}_{2}\), would be \(13 \times 12.01 + 18 \times 1.008 + 2 \times 16.00\).

Step 3 ：Calculate the molecular weight: \(13 \times 12.01 + 18 \times 1.008 + 2 \times 16.00 = 206.274\) amu.

Step 4 ：Final Answer: The molecular weight of ibuprofen, \(\mathrm{C}_{13} \mathrm{H}_{18} \mathrm{O}_{2}\), is approximately \(\boxed{206.3 \, \mathrm{amu}}\). Therefore, the correct option is (b).