Chapter 6 Flashcards
a buffer contains either:
- signifcant amounts of a weak acid and its conjugate base
2. significant amounts of weak base nn d its conjugate acid.
buffers:
solutions that resist pH change
adding a small amount of strong acid to a buffer converts a stoichiometric amount of base to the conjugate acid and ————- the ph of a buffer
decreases
adding a small amount of strong base to a buffer converts a stroichiometric amount of the acid to the conjugate base and ————- the pH of the buffer
increases
what factors effect the influence the effectiveness of buffer?
- the relative amounts of the acid and conjugate base
2. The absolute concentrations of the acid and conjugate base
when is a buffer most effective?
when the concentrations of acid and conjugate base are equal also when the conentrations of acid and conjugate base are highest
the relative concentrations of acid and conjugate base should not differ by more than a factor of —- in order for a buffer to be reasonably effective?
10
a buffer will be most effective when the ratio between acid:base is equal to what?
1
buffer capacity:
is the amount of acid or base that we can add to a buffer without destroying its effectiveness
acid-base titration:
a titrant in a burreete is added slowly to an analyte in a flask until the reaction is complete.
equivalence point:
the point in the titration when the number of moles of base is stoichiometrically equal to the number of moles of acid; the titration is complete
before the equivaklence point what is true?
prior to the equivalence point the analyte solution of known concentration in the flask is in excess
the volume at the equivalence point in an acid-base titration does not depend on whether the acid being tirtrated is a strong acid or a weak acid but on what?
only on the amount of acid present in solution before the titration begins and on the concentration of the added base.
at half neutralization pH=what?
pKa
indicator:
are weak acids establish equilibrium with the h2o and H30 in the solution, when the indicator turns colour that is the endpoint. if the indicator is precise enough the end point will be very close to the equivalence point
when pH is one unit or more below pKa….
idicator is the colour of HIn
when pH is one unit or more above pKa
indicator is the colour of IN
equilibrium constant is ———– dependent
temperature
solubility of a compound:
is the quantity that dissolves in a certain amount of liquid.
the lower the pH, the ——– the solubility
higher
precipitation:
will occur when the concentrations of the ions exceed the solubility of the ionic compound
how is the reaction quotient (Q)different than Ksp?
Ksp is the value of this product at equilibrium only whereas the Q is the value of the product under any conditions.
If Q< Ksp
the solution is unstaurated and more of the solid ionic compound can dissolve in the solution
if Q=Ksp
the solution is saturated, the solution is holding the equilibrium amount of the dissolved ions and additional solid does not dissolve in the solution
If Q>Ksp
the solution is supersaturated. Under most circumstances, the excess solid precipitates out of the solution
