Chapter 10: Acids and Bases Flashcards
(23 cards)
Arrhenius acids and bases?
Dissociate to form an excess of H+ and OH- in solution respectively
Bronsted-Lowry acids and bases?
Donate and accept a proton respectively
Lewis acids and bases?
Accept and donate an electron pair, respectively
What is an amphoteric species?
One that acts like an acid in a basic environment and a base in an acidic environment. Amphiprotic in a bronsted-lowry sense. Eg water, zwitterionic AAs
Nomenclature for:
anions ending in -ide?
anion ending in -ite?
anion ending in -ate?
hydro- -ic acid
- ous acid
- ic acid
What is autoionization? example?
When a compound reacts with itself to form ions. Ex water reacts with itself to form hydronium and hydroxide
What is Kw? Value?
Water dissociation constant. Kw = [H3O][OH] = 10^-14 at 298K
What does pH equal? pOH? How do they relate to each other?
pH = -log[H+]
pOH = -log[OH-]
At 298K, pH + pOH = 14
Quick math:
pH if [H+] = 0.0001? pOH?
if [H+] = 0.1? pOH?
10^-4, therefore pH = 4 and pOH = 10.
pH = 1 and pOH = 13
Approximate value for the log of a decimal between 1 and 10, eg. -log 1.8x10^-5?
-log (n x 10^m) = m - 0.n
so -log 1.8 x10^-5 = 5 - 0.18 = 4.82
Common strong acids encountered on the MCAT? Strong bases?
- HCl, HBr, HI, H2SO4, HNO3, HClO4
- NaOH, KOH and other Group IA metals with OH
Acid dissociation constant formula? Smaller Ka means?
Ka = [H3O+][A-] / [HA]
weaker the acid, less it will dissociate
Base dissociation constant formula? Smaller Kb means?
Kb = [B+][OH-] / [BOH]
weaker the base, less it will dissociations
What values generally characterize and weak acid and a weak base?
A Ka or Kb which is less than 1
What is Kw also equal to?
Ka x Kb, therefore a large Ka leads to a conjugate base with a very low Kb and vice versa
Normality of a polyprotic acid? eg of 2M H2SO4
H2SO4 has 2 acid equivalents x 2M, so 4N
Titrant vs Titrand?
small amount of solution with known concentration (titrant) is added to known volume of solution with unknown concentration (titrand) until equivalence point
Where is the equivalence point for a strong acid/strong base titration? For other titrations?
At pH 7. At whatever point the acid equivalents equal the base equivalents
Formula which allows for the calculation of the titrand concentration?
NaVa = NbVb, where Na and Nb are the normality of the acid and base and Va and Vb are the volumes
What are indicators? Color change point referred to as?
Weak acids and bases which have different colors in their protonated and deprotonated states. Must be a weaker acid or base than the acid or base being titrated, or they would change color immediately. Endpoint, should be very close to equivalence point
What does the half-equivalence point correspond to?
The pKa of an acid, when half is in its protonated state
What is the Henderson-Hasselbach Equation?
pH = pKa + log [A-]/[HA], therefore when [A-] = [HA] the pH = pKa -> the half-equivalence point. can be used for weak acid or weak base solutions: pOH = pKb + log [B+]/[BOH]
General buffering capacity of a buffer solution?
+/- 1 pH unit from the pKa
