General Chemistry Chapter 10: Acids and Bases Flashcards
Arrhenius acids
dissociate to produce an excess of hydrogen ions in solution
Arrhenius bases
dissociate to produce an excess of hydroxide ions in solution
Bronsted-lowry acids
are species that can donate hydrogen ions
Bronsted-lowry bases
species that can accept hydrogen ions.
Lewis acids
Electron pair acceptors
Lewis bases
Electron pair donors
Amphoteric species
those that can behave as an acid or base
Amphiprotic species
are amphoteric species that specifically can behave as a Bronsted-Lowry acid or Bronsted-Lowry base
What is the classic example of an amphoteric, amphiprotic species?
Water or conjugate species of polyvalent acids and bases
Water dissociation constant (Kw)
10^-14 at 298 K. It is only affected by changes in temperature.
pH and pOH
Can be calculated given the concentrations of H3O+ and OH- respectively . In aqueous solutions, pH + pOH = 14 at 298 K.
in solution, strong acids and bases
completely dissociate
In solution, weak acids and bases
do not completely dissociate in solution and have corresponding dissociation constants (Ka and Kb)
The conjugates of strong acids and bases have ___ conjugates
weak
Neutralization reactions form:
salts and sometimes water
Equivalent
one mole of the species of interest
Normality
concentration of acid or base equivalents in solution.
Polyvalent acids and bases
are those that can donate or accept multiple electrons. The normality of a solution containing a polyvalent species is the molarity of the acid or base times the number of protons it can donate or accept.
Titrations
Used to determine the concentration of a known reactant in solution.
Titrant
has a known concentration and is added slowly to the titrand to reach the equivalence point.
Titrand
has an unknown concentration, but a known volume
Half-equivalence point
midpoint of the buffering region in which half of the titrant has been protonated (or deprotonated); thus [HA] = [A-] and a buffer is formed.
Equivalence point
indicated by the steepest slope in a titration curve; it is reached when the number of acid equivalents in the original solution equals the number of base equivalents added; or vice versa.
Strong acid/strong base titrations have equivalence points at
pH=7
Weak acid/strong base titrations have equivalence points at
pH >7
Weak base/strong acid titrations have equivalence points at:
above or below 7, depending on the relative strength of the acid and base.
Indicators
are weak acids or bases that display different colors in their protonated and deprotonated forms
The indicator pH
should have a pKa close to the pH of the expected equivalence point
endpoint of a titration
is when the indicator reaches its final color
In polyvalent acid and base titrations
multiple buffering regions and equivalence points are observed
Buffering solutions
consist of a mixture of a weak acid and its conjugate salt or a weak base and its conjugate salt. They resist large fluctuations in pH.
Buffering capacity
refers to the ability of a buffer to resist changes in pH; minimal buffering capacity is seen within 1 pH point of the pKa of the acid in the buffering solution.
Henderson-Hasselbalch
quantifies the relationship between pH and pKa for weak acids and between pOH and pKb for weak bases.
When a solution is optimally buffered, pH = & pOH=
pH = pKa and pOH = pKb
