Characterisation Standards: What Counts as Proof of a New Compound · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Proof a compound is real

Science · Chemistry · ages 22-24
Name ______________________   Date ____________

  1. An exact mass matches the claimed formula within the stated tolerance. What does that rule out?

    • Every possible isomer
    • A different formula
    • Any impurity in the sample

  2. What does a fully assigned set of proton and carbon NMR spectra rule out?

    • A structural isomer
    • Any impurity at all
    • A wrong isotope ratio

  3. An isolated yield reported with no characterisation counts as a result.

    Circle one:   True   False

  4. Where should the molecular ion peak land for a claimed formula?

    • At the mass the formula predicts
    • At double the predicted mass, for safety
    • Wherever the tallest peak happens to sit

  5. Elemental analysis disagrees with the claimed formula. What does the mismatch say?

    • The balance needs new batteries
    • The formula is proven by effort alone
    • The sample is impure or the formula is wrong

  6. Which procedure line can another group repeat?

    • Purify the product until clean
    • Silica, 3 to 1 eluent, 10 mL fractions
    • Handle with care and hope for crystals

  7. Another group follows your written method and gets a different compound. Where do you look first?

    • The missing detail in the procedure
    • The brand of their glassware
    • The day of the week they ran it

  8. A draft experimental section claims a pure new compound, citing only a yield. Which gaps do you flag?

    • Missing adjectives about the product color
    • Missing thanks to the funding body
    • Spectra, formula proof and a purity method
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Answer key

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

Proof a compound is real W1-mt_WKhYUq-eyd-s1

  1. A different formula · An exact mass pins down the formula, so a different composition is ruled out. Isomers share the same formula, and one mass says nothing about purity.
  2. A structural isomer · Assigning every signal fixes how the atoms connect, which rules out a structural isomer. It cannot tell mirror-image forms apart, and it cannot promise the sample is free of every impurity.
  3. False · Yield without identity proof is a number without a claim.
  4. At the mass the formula predicts · Agreement between predicted and measured mass strengthens the identity.
  5. The sample is impure or the formula is wrong · Prediction versus measurement is the identity test; failure is a red flag.
  6. Silica, 3 to 1 eluent, 10 mL fractions · Grades, ratios, and volumes let strangers redo the work.
  7. The missing detail in the procedure · Repeatability fails first at the detail the author skipped.
  8. Spectra, formula proof and a purity method · Each missing item supported one part of the proof: identity, formula, purity.
Worksheet · LightMySky