Aqueous Equilibria lecture slides Flashcards
common ion effect
the shift in the position of an equilibrium upon addition of a substance that provides an ion already involved in that equilibrium
buffers
solutions that resist changes in pH when limited amounts of acid or base are added
-the resistance to change in pH arises from the presence of appreciable concentrations of weak acid and its conjugate (weak) base
how does a buffer work
neutralizes added strong acid/base
buffer needs sources of protons (HA) to…
neutralize incoming bases
buffer needs sinks of protons (A) to…
neutralize incoming acids
formula for calculating pH of buffers of known conc
pH=pKa + log[base/acid]
buffer capacity
molar amount of acid or base which the buffer can handle without significant changes in pH
in buffers large shifts in the acid/base conc=
small changes in pH
titration
a procedure for determining the concentration of a solution by allowing a carefully measured volume of it to react with a sol of another substance(standard sol) whose conc. is known
equivalence point
the point at which stoichiometrically equivalent quantities of acid and base have been mixed together
-max slope
before ep whats in excess
h3o
after ep whats in excess
oh
weak acid/strong base titration
-what are the major and minor species before addition of base at step 1)
major: HA (and H2O)
minor: H3Osn A-
weak acid/strong base titration
-what are the major and minor species at the buffer region at step 2)
major - ha, a (and water)
minor- h3o
-pH determined by henderson-hasselbach eqn
when [HA]=[A], pH=
pKa (halfway to ep)
weak acid/strong base titration
-what are the major and minor species at the ep at step 3)
major- a and h20
minor-oh and ha
-all HA converted to A-
-sol is basic bc of presence of A-
weak acid/strong base titration
-what are the major and minor species past the ep at step 40
major- A, OH, and h2o
minor- none (Strong base)
