Flashcards in Chapter 10: Acids and Bases Deck (23):
1
Arrhenius acids and bases?
Dissociate to form an excess of H+ and OH- in solution respectively
2
Bronsted-Lowry acids and bases?
Donate and accept a proton respectively
3
Lewis acids and bases?
Accept and donate an electron pair, respectively
4
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
5
Nomenclature for:
anions ending in -ide?
anion ending in -ite?
anion ending in -ate?
hydro- -ic acid
-ous acid
-ic acid
6
What is autoionization? example?
When a compound reacts with itself to form ions. Ex water reacts with itself to form hydronium and hydroxide
7
What is Kw? Value?
Water dissociation constant. Kw = [H3O][OH] = 10^-14 at 298K
8
What does pH equal? pOH? How do they relate to each other?
pH = -log[H+]
pOH = -log[OH-]
At 298K, pH + pOH = 14
9
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
10
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
11
Common strong acids encountered on the MCAT? Strong bases?
-HCl, HBr, HI, H2SO4, HNO3, HClO4
-NaOH, KOH and other Group IA metals with OH
12
Acid dissociation constant formula? Smaller Ka means?
Ka = [H3O+][A-] / [HA]
weaker the acid, less it will dissociate
13
Base dissociation constant formula? Smaller Kb means?
Kb = [B+][OH-] / [BOH]
weaker the base, less it will dissociations
14
What values generally characterize and weak acid and a weak base?
A Ka or Kb which is less than 1
15
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
16
Normality of a polyprotic acid? eg of 2M H2SO4
H2SO4 has 2 acid equivalents x 2M, so 4N
17
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
18
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
19
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
20
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
21
What does the half-equivalence point correspond to?
The pKa of an acid, when half is in its protonated state
22
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]
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