Unit 8: Acids And Bases Flashcards
Water autoionization constant?
K_w = 1.0 * 10^-14 = [H3O+][OH-], where pH = pOH = 7 at 25 degrees C
Why in water, pH = pOH?
Because water has the same potential to release or accept a proton.
K_a = ?
([H3O+][A-])/[HA], [A-] is the concentration of the conjugate base of the unionized acid, [HA] is the concentration of weak acid that hasn’t ionized yet.
K_b?
([OH-][HB+])/[B], [HB+] is the concentration of conjugate acid.
If you have a solution of the same concentration of strong acid and base, then the products will be?
H2O (l)
In a strong acid and base solution, the pH of the resulting solution may be determined from the concentration of?
Excess reagent.
If you mix a weak acid and strong base at equal concentrations, then the reaction equation?
HA (aq) + OH- (aq) <-> A- (aq) + H2O (l)
Buffer solution?
An excess of weak acid [HA] compared to strong base [OH-].
!!!!!!!How do you determine the pH of a buffer?
The Henderson-Hasselbalch (H-H) equation:
If the strong base is in excess, how do you compute the pH of the solution?
Determining the moles of excess [OH-] and the total volume of the solution.
If a weak base and a strong acid are mixed in equal concentrations, the reaction equation?
B(aq) + H3O+ (aq) <-> HB+ (aq) + H2O (l)
If a weak base is in excess with a strong acid inside, then what type of solution is formed?
A buffer solution and the pH can be determined by the H-H- Equation.
If a strong acid is excess in a solution with a weak base, how do you compute the pH?
By determining the moles of excess [H3O+] and the total volume of solution.
For titrations of weak acids and bases, the half-equivalence point tells us?
Each species in the conjugate acid-base pair are equal in concentration, [HA] = [A-]. This means that pKa = pH
Strong acids have weak/strong conjugate bases?
Weak, since they are stabilized by electronegativity, inductive effects, and resonance.
An increase in electronegativity increase/decrease acid strength?
Increase
pH > pKa, then you have?
More base
If pH < pKa, then you have?
More acid.
K_b is a base in?
Water
The larger the pK_b, the weaker/stronger the base?
Weaker
The larger the pK_a value, the weaker/stronger the acid?
Weaker
pK_a = ?
-log(K_a), which is an inverse relationship
K_w = ?
K_a * K_b
If you have a strong acid or strong base, do you need to worry about equilibrium?
No
Is X+ a conjugate acid/base of a weak acid/base?
Acid, base. Opposite for Y-
•Acidic+neutral =
•Basic+neutral =
•Neutral+neutral =
•Acidic+neutral = acidic
•Basic+neutral = basic
•Neutral+neutral = neutral
Buffer?
Any solution that maintains an approx constant pH despite small additions of acid and base
Acid buffer?
Consists of a weak acid and its conjugate base supplied as sat. It buffers on acidic side of neutral
Base buffer?
Consist of weak base and conjugate acid supplied as a salt. Buffers on the basic side of neutral
In a buffer reaction, what happens to the products?
The conjugate acid or base follows its properties (e.g., donates or accept proton) to maintain pH due to stress in the products side.
How many conjugates do you have in buffers?
Two conjugates.
