Acids and Bases Flashcards
Arrhenius Acid vs Base
Acid: produces H+
Base: produces OH-
Bronsted Lowry Acid vs Base
Acid: donates H+
Base: accepts H+
Lewis Acid vs Base
Acid: accepts e - pair
Base: donated e - pair
Strong vs Weak acid
Strong: weaker bonds; complete dissociation
Weak: stronger bonds; partial dissociation
What determines acid strength?
1.) Orbital overlap; the more similar the bond the stronger it is
2.) Electron density goes to stronger bonds
3.) Acids that contain O are weaker than other acids
What is meant by “impacts pH”?
Can steal or give H+ to water
Amphetric
Can act as an acid or base (water)
Sig figs with logs
log (x) = y The number of sign figs in the input determines the number of decimal places in the output
Ka
The equilibrium constant of something behaving as an acid in water
Kb
The equilibrium constant of something behaving as a base in water
What does pKa and pKb mean?
The higher the K more the favoring of products, so the strength of acid/base increases. The lower the pK the stronger the acid.
Salt
Ionic compound
Can metal ions (cations) affect pH?
No, treat as spectators
What do conjugate bases of strong acids/bases do?
Do not affect the pH of H20
What do conjugate bases of weak acids do?
Affects pH of H20 by accepting H+ (basic ion)
What do conjugate acids of weak bases do?
Affects pH of H20 by donating H+ (acidic ion)
How to determine if something is an acid, base, or salt?
1.) Determine its conjugate
2.) Covalent compounds = neutral/
3.) Metal hydroxide = strong base
4.) Acid with O in it = weak acid
Polyprotic acid
Acids with two or more acidic H + ions
How to find pH of strong acid with [acid]?
[acid] = [H3O+], pH = -log[H3O+]
How to find pH of strong base with [base]?
n[M(OH)n] = [OH-], pOH = -log[OH-], pH= 14-pOH
How to find pH of weak acid with [acid]?
ICE[acid] to find [H30+] eq using Ka, pH = -log[H30+]
How to find pH of weak base with [base]?
ICE[base] to find [OH-] eq using Kb, pOH = -log[OH-], pH = 14 - pOH
How to find pH of salt with [salt]?
1.) Split into ion and determine if a/b/n
- acidic salt, treat as weak acid, get Ka from conj. base Kb
- basic salt, treat as weak base, get Kb from conj. acid Ka
- neutral, pH = 7
What does 0.1mol/L equal
0.1mmol/ml
How to get the following for weak acid with strong base -
A. Initial pH
B. Buffer region
C. Equivalence point
D. Overtitration
A. Only HA is present, find pH of weak acid
B. HA and A- present, find pH with PUG followed by ICE/HH
C. Only A- present, find pH with PUG followed by ICE, need Kb of conjugate base and consider dilution
D. OH- and A- present, approximate as strong base PUG and consider dilution
How to get the following for weak base with strong acid -
A. Initial pH
B. Buffer region
C. Equivalence point
D. Overtitration
A. Only base is present, find pH of weak base
B. HB+ and B+ present, find pH with PUG followed by ICE/HH
C. Only HB+ present, find pH with PUG followed by ICE only for equilibrium with Ka and consider dilution
D. H30+ and HB+, use PUG, approximate as strong acid and consider dilution
Buffers
Resist change in pH over a pH range of 2 values by consuming incoming acids with a base and vice versa, then re-equilibrating
How can you make a buffer?
1.) Add acid and conjugate base pair together
2.) Add until weak acid/base and conjugate acid/base are left
How can you find the concentration of an acid or base?
1.) Use stoichiometry to find the equivalence point (use L of one chemical and mole-to-mole ratio to get M)
OR
2.) Use initial pH and experimentally determined Ka (use ICE table and add/subtract Ka/Kb and use Ka/Kb = [A][B]/[C] and solve for y to get M
How can you get Ka/Kb given pH and M?
1.) Net ionic equation with water
2.) Use 10 to the -pH/pOH for Ka/Kb
3.) Set up ICE using M and +/- Ka/Kb
4.) Solve for Ka/Kb using Ka/Kb = [A][B]/[C]
Secondary Way
(10 to the - pH) squared / (M - 10 to the -pH)
How can you find pH of polyprotic acids?
1.) pH= -log[M]
2.) Write out last dissociation
3.) Use ICE table with +/- M and Ka/Kb and solve for x
4.) You now have [H3O]/[OH] and can solve for pH
How can you find pH given ml/M of analyte/titrant?
1.) Multiply ml by M to get mmol
2.) Net ionic equation mixing analyte/titrant (take out spectators)
3.) Use PUG table using mmol and +/- mmol titrant
4.) Use HH to calculate pH
How can you get ml to make a buffer given g, M, and desired pH?
1.) Get pKa/pKb using M
2.) Use HH with pKa/pKb and pH. Solve for (A-/HA or HB/B) and exponentiate to get acid:base ratio
3.) Convert g to ml x mole to mole ratio x M to get ml
How can you find acid:base ratio for buffer, given Ka/Kb?
1.) Get pH using Ka/Kb
2.) +/- 1 pH to find out range
3.) Use either end of +/- 1 as pH and the pH as pKa in HH equation and solve for (A/HA or HB/B) by expotentiating. Do for both extrema
What should you be sure of when calculating pH of a base?
Account for moles and multiply by them
Insoluble
Dissolves to a small extent
Soluble
Dissolves to a large extent
The larger the Ksp…
The more the compound dissolves
How can you find the conc of an ion in a saturated compound?
1) Set up ICE table with dissociation (be sure to account for moles)
2) Ksp = [X] to the n [Y] to the m
3)Set it equal to given Ksp and solve for x
4) Multiply it by moles of ion if needed
Qsp/Ksp rules
Qsp = Ksp saturated solution; no more ions can be dissolved
Qsp < Ksp unsaturated solution; more ions can be dissolved
Qsp > Ksp supersaturated solution; no more ions will dissolve and a precipitate forms
Molar solubility
Molarity of a saturated solution, max concentration of your compound
What is solubility reported in?
g/1 L
How can you find solubility given molar solubility?
Multiply molar solubility by molar mass of compound
How can you predict if a precipitate forms in a solution?
1) Write out equation and use the following for the potential solid that forms
2) Use M1V1 = M2V2, with V total for V2 for first ion (metal)
3) Use M1V1 = M2V2 for OH and multiply M by moles
4) Qsp = [Metal] to n and [OH] to m
5) Determine if precipitate forms given Ksp/Qsp rules
How can you do a common ion effect problem?
1) set up ICE table for compound in water and in a solution
2) Use just x for water and molarity +/- X for solution
How does pH affect solubility?
If pH of conj acid/base is greater than 7 then solubility decreases
If pH of conj acid/base is less than 7 then solubility increases
