Mass Spectrometry: Ionisation Methods and Mass Analysers · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Making ions and sorting them by mass

Science · Chemistry · ages 20-21
Name ______________________   Date ____________

  1. A spectrum is full of fragments with no molecular ion. Which ionisation was likely used?

    • A soft method that keeps molecules intact
    • No ionisation at all
    • A hard method that shatters the molecule

  2. What are the three jobs of a mass spectrometer in order?

    • Make an ion, sort by mass to charge ratio, count it
    • Sort by colour, weigh on a scale, photograph it
    • Freeze the sample, melt it, boil it

  3. In a magnetic sector analyser, heavier ions bend less and lighter ions bend more.

    Circle one:   True   False

  4. How does a time of flight analyser separate two ions?

    • By giving both the same push and timing the race, so lighter ions arrive first
    • By bending them in a magnet into different circles
    • By staining them different colours and sorting by eye

  5. Two ions share the same mass but one carries double the charge. How do their paths compare?

    • Both bend identically, since only mass matters
    • The doubly charged ion bends more strongly
    • The doubly charged ion flies straight with no bend

  6. What does higher resolving power let an analyst do?

    • Detect brighter colours in the sample
    • Distinguish masses that sit closer together
    • Run the instrument with no vacuum at all

  7. A very heavy molecule falls outside the working mass window. How do multiply charged ions help?

    • Extra charges make the molecule lighter in reality
    • They change the molecule into a different lighter compound
    • Several charges make it behave like a lighter singly charged ion, so it lands inside the window

  8. A spectrum shows no molecular ion. What should the analyst change to reveal the molecular mass?

    • Switch to a softer ionisation method that keeps the molecule intact
    • Crank up the hardness to shatter the molecule further
    • Remove the detector so fragments stop appearing
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Answer key

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

Making ions and sorting them by mass W1-mt_JTTb7FM1L4-s1

  1. A hard method that shatters the molecule · Hard ionisation breaks the molecule apart, so the intact mass peak vanishes.
  2. Make an ion, sort by mass to charge ratio, count it · Ionise first, then sort the ions, then count what lands.
  3. True · The radius grows with mass, so heavy ions curve gently and light ones curve sharply.
  4. By giving both the same push and timing the race, so lighter ions arrive first · Equal pushes give lighter ions more speed, so arrival time reports the mass.
  5. The doubly charged ion bends more strongly · Charge sits underneath in the radius, so doubling it tightens the circle.
  6. Distinguish masses that sit closer together · Finer sorting splits nearly identical ratios into separate landing spots.
  7. Several charges make it behave like a lighter singly charged ion, so it lands inside the window · Sorting answers to the ratio, so spreading mass over several charges shrinks the ratio.
  8. Switch to a softer ionisation method that keeps the molecule intact · Gentler ionisation preserves the intact molecule, so its mass peak appears.
Worksheet · LightMySky