Acid-Base Lab
• Most people are familiar with the idea
that leaves, flowers and fruits have
different pigments.
• The best known is chlorophyl as it
helps with photosynthesis.
• But once you scratch the surface you
will find a whole rainbow underneath
the green.
• Other pigments have important roles
• Carotene and Xanthophyll aid in
photosynthesis as well as play a role in
the metabolism of plants.
• As for Anthocyanins, the jury is still
out, but scientists think they might be
instrumental in blocking UV radiation
• From the Greek antos: flower; kyanos:
• They are a class of pigments belonging
to a larger group known as flavonids.
• They have been used since antiquity as
dyes, and contribute to the coloration
of petals, fruits bracts and leaves.
• They can be found in a variet of
places in plants, depending on
thier specific role.
• Often they appear in quite
attractive colors, so they will
often times exist in flowers and
berries, suc as poinsettias, roses
and blue/raspberries.
• While there is some pharmacutical
evidence that anthocyanins may
contain antioxidants that are
beneficial for your health, we will be
focussing on one of their other
properties; they ability to detect
• a weak-acid indicator may be represented as HIn where In = indicator.
• HIn H+ + In- a reversable reaction where both HIn and In- are
• a. colors display because HIn and In- are different colors.
• b. when acid is added, In- takes protons and pushes the reaction to
the left.
• c. when base is added, the OH- from the base combine with H+
making more HIn and pushing the reaction to the right
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