Question on: JAMB Chemistry - 2024

An organic compound contains 53.1% Carbon, 6.2% Hydrogen, 12.4% Nitrogen, and 28.3% Oxygen by mass. What is the molecular formula of the compound if its vapour density is 56.5? [C = 12, H = 1, N = 14, O = 16]

C₅H₇NO₂

C₅H₆NO₂

C₃H₆NO₂

C₃H₇NO₂

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Correct Option: A

Here's how to determine the molecular formula:

1. Assume a 100 g sample: Percentages equal grams: Carbon 53.1 g, Hydrogen 6.2 g, Nitrogen 12.4 g, Oxygen 28.3 g.

2. Calculate moles: Carbon 53.1/12 = 4.425 mol, Hydrogen 6.2/1 = 6.2 mol, Nitrogen 12.4/14 ≈ 0.886 mol, Oxygen 28.3/16 ≈ 1.769 mol.

3. Determine the empirical formula: Divide all by smallest number (0.886): C₅H₇NO₂.

4. Check with vapour density: Matches molecular formula C₅H₇NO₂.