Isomerism: Same Formula, Different Molecule · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Same formula, different molecule

Science · Chemistry · ages 16-17
Name ______________________   Date ____________

  1. Butane and methylpropane share C4H10. What are they?

    • The same substance drawn twice
    • Chain isomers with different skeletons
    • E and Z isomers

  2. What does a molecular formula tell you?

    • How the atoms connect
    • Which atoms are present and how many of each
    • Which isomer you hold

  3. Propan-1-ol and propan-2-ol are which kind of isomers?

    • Chain isomers
    • Position isomers, with the group on different carbons
    • Functional group isomers

  4. A molecular formula alone is enough to identify which isomer you hold.

    Circle one:   True   False

  5. Ethanol and dimethyl ether share C2H6O. Why do they behave so differently?

    • They belong to different families, alcohol versus ether
    • One has more atoms than the other
    • One is a mixture and the other is pure

  6. Why can a double bond produce stereoisomers?

    • Single bonds rotate freely but the pi bond locks the molecule
    • Double bonds contain fewer electrons
    • Double bonds always break and reform

  7. A student calls propan-1-ol and propan-2-ol chain isomers. What is the error?

    • They are position isomers, since only the group position differs
    • They are not isomers at all
    • They are E-Z isomers of propene

  8. Two groups of top priority sit on opposite sides of a double bond. Is it E or Z?

    • Z, because opposite means zusammen
    • Neither, priority only matters for chains
    • E, because the top groups sit on opposite sides
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Answer key

For grown-ups. Fold this page away before handing over the rest.

Same formula, different molecule W1-mt_DvD0coeKZe-s1

  1. Chain isomers with different skeletons · Their skeletons connect differently, so they are chain isomers.
  2. Which atoms are present and how many of each · A molecular formula counts atoms but hides the connections.
  3. Position isomers, with the group on different carbons · Same skeleton and group, different carbon, means position isomers.
  4. False · One formula can describe several different molecules.
  5. They belong to different families, alcohol versus ether · Same atoms arranged as different functional groups behave nothing alike.
  6. Single bonds rotate freely but the pi bond locks the molecule · The pi bond stops rotation and freezes arrangements in place.
  7. They are position isomers, since only the group position differs · Identical skeletons with a moved group means position isomerism.
  8. E, because the top groups sit on opposite sides · Opposite sides for the top ranked groups gives E.
Worksheet · LightMySky