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In so far a scientific statement speaks about reality, it must be falsifiable: and in so far as it is not falsifiable, it does not speak about reality.

Karl Raimund Popper (1902 - 1994)
Karl Raimund Popper (1902 - 1994)
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  • Harprit

    5 Oct 2026

    Hello Geoff, In R2.3.4, the IB guide talks about Le Chatelier's Principle to physical equilibria and gives a (g) / (aq) as an example. A very old IB question came up looking at a (l) / (g), and what happens when you increase the volume of liquid....

    R2.3 The extent of chemical change

  • Paul

    Site author
    1 Oct 2026

    Me too! As far as I know, there are no other issues with sodium hydroxide in the burette. My students frequently do it that way round. We just make sure that we don't leave the sodium hydroxide in the burette, and we rinse it out afterwards. The etching...

    Acid-alkali titration

  • Austin

    30 Sep 2026

    In general, I find it easier to identify the colourless to pink colour change rather than pink to colourless.  Is there any major issue with switching the acid and base other than that the sodium hydroxide may cause etching or other damage to...

    Acid-alkali titration

  • Paul

    Site author
    30 Sep 2026

    Hi John Yes, that's correct.And I can confirm that the guide, Reactivity 3.2.2, says: Deduce redox half-equations and equations in acidic or neutral solutions. I believe candidates might be asked to balance a...

    R3.2 Oxidation & reduction

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