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B You should have written down something similar to the following.
or
Where does the equilibrium lie in the following reaction?
C An acid always loses a proton to the conjugate base of any weaker acid with a
higher
pK
a
. Ethanoic acid is the stronger acid with a
pK
a
of 4.76 compared with 9.31 for
hydrogen cyanide. Therefore, the equilibrium lies toward the right.
What will happen in the reaction of ethyne with hydroxide?
D H
2
O is the stronger acid with the lower
pK
a
, and the reaction will not occur as it is
drawn. Instead, the reverse reaction will occur. This is because the acetylide carbanion
is a stronger base than hydroxide.
There is another way to decide on acid-base reactivity. For a reaction to be
spontaneous, the products must be more stable (less reactive) than the reactants.
See Program 17.
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