(A) When a 0.5120 g sample of a gaseous hydrocarbon was burned in excess oxygen, 1.687 g CO₂ and 0.4605 g H₂O were obtained. The density of the compound, in its vapor form, is 1.637 g/L at 25 °C and 101.3 kPa. Determine the molecular formula of the hydrocarbon, and draw a plausible structural formula for the molecule.

(B) An organic compound contains only C, H, N, and O. When the compound is burned in oxygen, with appropriate catalysts, nitrogen gas (N₂), carbon dioxide (CO₂), and water vapor (H₂O) are produced. A 0.1023 g sample of the compound yielded 151.2 mg CO₂, 69.62 mg H₂O, and 9.62 mL of N₂(g) at 0.00 °C and 1.00 atm. The density of the compound, in its vapor form, was found to be 3.57 g L^-1 at 127 °C and 748 mmHg. What is the molecular formula of the compound?