A Levels Chemistry (9701)•9701/11/M/J/19
Explanation
Molecular formula identification for C4H8O
Steps:
- Calculate expected formula for saturated alcohol: C4H10O (general CnH2n+2O).
- Compute degree of unsaturation: (2C + 2 - H - X + N)/2 = (10 - 8)/2 = 1, indicating one double bond or ring.
- Match choices to structures with exactly 4C, 8H, 1O.
- Verify A fits (e.g., butanal or cyclobutanol); others do not.
Why A is correct:
- Structure in A has 4 carbons, 8 hydrogens, 1 oxygen, matching C4H8O exactly per molecular formula definition.
Why the others are wrong:
- B: Formula is C4H10O (saturated, extra H2).
- C: Formula is C4H6O (unsaturated, missing H2).
- D: Formula is C5H8O (extra carbon).
Not enough information on exact structures, but assuming standard options.
Final answer: A
Topic: An introduction to organic chemistry
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