Chapter 21 - Acids, Bases, and Buffers
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whats a bronsted lowry acid and base
acid donates protons base accepts protons
how does water exist in solution
as an equilibrium mixture of H plus ions and hydroxide ions and water
give the equation for Kw
[H+][OH-] = Kw
why does the Kw equation not contain water
because the concentration of water is so great that it can be considered constant Kw is the product of the reactions equilibrium constant and the concentration of water
why is pure water neutral despite its pH
in pure water the hydrogen and hydroxide ions are always in a 1 to 1 ratio
is the dissociation of water exo or endo
endo because bonds are breaking
what happens to waters pH if the temperature increases
the forward reaction is endothermic so the concentration of H+ ions increases and thus the pH decreases into an acidic range
give the equation for pH
-log[H+]
how are the concentrations of H+ and OH- related given a constant temperature
inversely proportional
what is a strong acid/alkali
one which completely dissociates in aqueous solution
what is a weak acid/alkali
one which forms an equilibrium mixture when it dissociates in solution
what is a titration used for and how
finding the concentration of a solution by gradually adding a solution of a known concentration with which the first solution reacts
where is the solution of known concentration in a titrtion
in the burette
what is the equivalence point
the point at which all of the solution in the flask has been neutralised
what does the equivalence point look like on a titration curve
the region with the most vertical gradient
where is the equivalence point on a strong acid strong base titration
7
where is the equivalence point on a weak acid strong base titration
apx. 8
where is the equivalence point on a strong acid weak base titration
apx. 6
where is the equivalence point on a weak acid weak base titration
7
which titration curves have a buffer region
those which involve a weak acid and strong base or a strong acid and weak base
define the end point
the volume of acid or base added when the indicator just changes colour
name the qualities a suitable indicator must exhibit
colour change must be sharp at the end point end point must be the same as the equivalence point indicator must have a distinct colour change
define a buffer solution
a solution which resists changes in ph when small amounts of acid or base are added
what is the half neutralisation point
the point halfway between the equivalence point and 0