CHM110H5 Lecture Notes - Hydronium, Lone Pair, Equivalence Point
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Date: 31 October, 2012
1. Trifluoracetic acid will be stronger because it contains fluorine substitutes which are more
electronegative than chlorine atoms. This causes a major difference between the electro-
negativities of the atoms which results in easy dissociation of hydrogen from the acid to bond
with water molecules and form hydronium ions.
2. pKA of HCN = 9.4 pKA of HF= 3.17
Since HF is a stronger acid than HCN (which can be inferred from the pKA), HF will act as the
proton donor and HCN will act as a base and accept the protons from HF
From the lewis structure of HCN, , It can be concluded that the extra proton
from Hydronium will attach to the lone pair of electron and establish a bond.
3. Acid-Base indicators are used to detect the equivalence points of a titration. They must be weak
acid/base themselves and the HIn (protonated form) and In- must have different colors. Also,
the colors must be intense so that the concentration of the indicator can be low. The end point
of the indicator should be close to the equivalence point of titration (especially important when
one of the electrolytes is weak)
4. pH = 5.9
Species present when the reaction is at equilibrium are
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