pKa as a Predictive Tool in Organic Chemistry · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

One number that predicts proton swaps

Science · Chemistry · ages 18-19
Name ______________________   Date ____________

  1. By what factor does acid strength change across one pKa unit?

    Answer: ______________

  2. Two acids face off in a proton transfer. Which side wins?

    • The side with the larger pKa
    • The side with the smaller pKa
    • Neither side ever dominates

  3. What is the first factor you check when explaining an acidity difference?

    • Induction
    • Hybridisation
    • Element

  4. Why are the alpha hydrogens of a ketone far more acidic than alkane hydrogens?

    • Tables never list ketone values
    • Its anion spreads charge onto oxygen
    • Alkanes refuse all bases

  5. A proton transfer has a pKa gap of 3. By what ratio does the winning side dominate?

    Answer: ______________

  6. A target proton has pKa 16. Can a base whose conjugate acid has pKa 15 remove it cleanly?

    • No, its conjugate acid is stronger than the target acid
    • Yes, any charged base works
    • Yes, since all transfers are fast

  7. A student claims the stronger acid always carries the larger pKa. True or false, and why?

    • True, big pKa means strong acid
    • False, a strong acid has a small pKa
    • True, when the solvent is water

  8. Rank these nitrogen bases from weakest to strongest: amides, anilines, aliphatic amines.

    • Amides, then anilines, then aliphatic amines
    • Anilines, then amides, then aliphatic amines
    • Aliphatic amines, then anilines, then amides
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Answer key

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

One number that predicts proton swaps W1-mt_fI03mNIC_m-s1

  1. 10 · The pKa scale is logarithmic, so each unit multiplies strength by ten.
  2. The side with the larger pKa · Equilibrium favours the weaker acid and weaker base.
  3. Element · Walk the fixed order and stop at the first difference.
  4. Its anion spreads charge onto oxygen · Delocalisation at the end of the checklist settles it.
  5. 1000 · Three units of gap mean ten cubed, which is one thousand.
  6. No, its conjugate acid is stronger than the target acid · Without the higher pKa on your side, the proton stays put.
  7. False, a strong acid has a small pKa · Low pKa means eager proton donor.
  8. Amides, then anilines, then aliphatic amines · Read the ladder backwards: weaker conjugate acid means stronger base.
Worksheet · LightMySky