Acid - Base Equilibrium Flashcards
pKw, pH, pOH
Equations
- pH= -log([H3O+])
- Also H+ = 10^-pH
- pOH= -log([OH-])
- OH- = 10^-pOH
- pKw = pH + pOH = -log([OH-] [H3O+])
- Ka * Kb = Kw
pH, pOH
How to decide concentration of H3O+ or OH-
- if in strong acid just that from the acid because self-ionization of water is negligible
Conjugate Base/Acid
Hydrolysis Rxns
- Acid - base rxns between ions(from salts) and H2O molecules
- May react with water in a/b rxn
Conjugate Base/Acid
pH vs H3O+ / OH- concentration
- 7: [H30+] = [OH-]
- <7: [H30+]
>[OH-] - > 7: [H30+] < [OH-]
Conjugate Base/Acid
Determining Conjugate Base/Acid
- If acid, then find with extra electron (goes from donator to acceptor) ⇒conj base
- If base, then find with less electron (goes from acceptor to donator) ⇒ conj acid
Acid, Bases, and Acid-Base Equilibria
Acid
- Proton Donor
Acid, Bases, and Acid-Base Equilibria
Base
- Proton Acceptor
Acid, Bases, and Acid-Base Equilibria
Strong Acids
- HCl
- HBr
- HI
- HNO3
- H2SO4
- HCLO4
* Complete Ionization: →
Acid, Bases, and Acid-Base Equilibria
Weak Acids
- CH3COOH
- NH4+
* Partial Ionization: ⇌
Acid, Bases, and Acid-Base Equilibria
Strong Bases
- Group 1A and 2A with Hydroxides
- Complete Ionization: →
Acid, Bases, and Acid-Base Equilibria
Weak Base
- NH3
- Partial Ionization: ⇌
Acid, Bases, and Acid-Base Equilibria
Ka/ Kb
- Acid/Base Ionization Constant
Acid, Bases, and Acid-Base Equilibria
Relation bet a/b and conj a/b
- Stronger the original, weaker the conjugate and vice versa
- Favored in the direction = stronger to weaker
Acid, Bases, and Acid-Base Equilibria
Kw
- Ion product of H2O
- = [H3O+][OH-] = 1.0 * 10^-14 M
- both H3O+ and OH- have concentrations of 1.0 * 10^-7
Acid, Bases, and Acid-Base Equilibria
How to deal with weak Acid/ Base equilibria
- Use ICE Table
- If M(a/b)/K(a/b) > 100, then [A/B]≈ Eq. value
Acid, Bases, and Acid-Base Equilibria
Which ions hydrolyze
- Weak acids or bases hydrolyze appreciably
- Strong a/b form neutral solutions
Acid, Bases, and Acid-Base Equilibria
Relationship between weak and strong a/b
- Weak Acids and Strong Bases = basic
- Strong Acids and Weak Bases = acidic
- Weak a + b = any of them
Common Ion Effect
Common Ion Effect
ASK ABT THIS
- Supression of ionization of weak acids or weak bases by presence of common ion from a strong electrolyte
Buffer Solutions
Definition
Solution that changes pH only slightly when small amounts of strong acid or base added
* Usually contain: weak acid/base with salt
Buffer Solutions
Buffer Rules
- ratio of [conjugate base/ acid] / [weak acid/ base] between .10 and 10
- both [conjugate base/ acid] and [weak acid/ base] exceed Ka by factor of 100+
Buffer Solutions
Henderson–Hasselbalch equation
pH = pKa + log([conj base]/ [weak acid])
Buffer Solutions
Heylman equation
pOH = pKb + log([conj acid]/ [weak base])
Buffer Solutions
Buffer Action
- best buffer is when [conj acid / base] = [weak base / acid] → best buffer!
Buffer Solutions
Effective Buffer Range
- Approximately when pH = pKa ± 1 pH-unit
Acid-Base Titrations
Analyte
- solution of unknown concetration
Acid-Base Titrations
Titrant
Solution with known concentration
Acid-Base Titrations
Equivalence point
AKA Stoichiometric pt
- # of moles of H3O+ = # of moles of OH-
Indicators
What are they
A weak organic acid that has a different color than conjugate base
Indicators
Relation bet. [HIn] and [In-]
- equal means intermediate color
- [In-]/[HIn] >10: solution will be color of In-
- [In-]/[HIn] < .10: solution will be color of HIn
Indicators
Endpoint
- Point where indicator changes color
Indicators
Equation
- Ka/[H3O+] = [In-]/[HIn]
