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THE MCAT-CHEM 2

ACIDS, BASES, BUFFERS

QuestionAnswer
Arrhenius acid produces H
Arrhenius base produces OH
Bronsted and Lowry acid donate H
Bronsted and Lowry base accept H
Lewis acid accept pair of electrons
Lewis base donates pair of electrons
Strong acid... weak c.b.
Strong base... weak c.a.
Weak acid... do NOT necessarily have strong c.b.
pH + pOH= 14
Strong acid / base has ______ dissociation because conjugate species is ______. complete / stable
A weak acid / base has _______ dissociation because conjugate species is _____. partial / fairly stable
For a strong acid/base, the conc. of H / OH produced is the same as? original concentration of acid / base
Strong acid: 0.01M H = 0.01 M of original acid
Relate Ka, pKA for strong acid larger Ka, smaller pKA, stronger acid
Relate Kb, pKb for strong base larger Kb, smaller pKb, stronger base
pH > pKa deprotonated
pH < pKA protonated
amphoteric vs. ampipathic -amphoteric = act as either an acid / base -ampipathic = hydrophobic / hydrophilic
Why is Ka so larger for strong acids? complete dissociation
Shortcut equation to determine pH for weak acid / base reagent? pH = 1/2pKa - 1/2 log [HA]
Henderson - Hasselbalch Equation pH = pKa + log (conj. base) / (conj. acid) --> use conc. or mole quantities
Where in graph is buffer most important? 1/2 equivalence point
What characteristics for 1/2 E.P. for titration of acid with strong base? -pH = pKa -moles acid = moles conjugate base -[acid] = 1/2[base]
Equivalence point moles acid/base = moles titrant
In the titration of an acid with a strong base, what is the predominant species at the E.P.? 100 % A-
What is a good buffer? pH = pKa +/- 1
For Haloacids, within a group, what dictates acid strength? halogen size and bond length
For haloacids, within a period, what dictates acid strength? electronegativitiy of atom
Why do more oxygens increase acid strength? double bonded oxygens are EWG making electron deficient
Nonmetal oxide is a ____ acid. Metal oxide is a _____ base. lewis
Nonmetal hydroxide is a _____ acid. Metal hydroxide is a _____ base. bronsted and lowry
Calculate Normality. acid molarity * number of protons
Which proton removed in a polyprotic acid is always the most acidic? first
Will adding water change the pH of a buffered solution? NO --> equally dilutes weak acid and conj. base
A buffer is rougly equal conc. of what? weak acid and weak conj. base
The ratio of weak acid: conj. base for a buffer cannot exceed? 10:1 (in favor of either)
What does a buffer create? relatively constant pH through resisting changes caused by titration
the Pka of the weak acid for a buffer should be close to what? the desired pH of the solution
base + acid = salt and water
Strong acid + strong base, pH = 7
strong acid + weak base, pH = < 7
strong base + weak acid, pH = > 7
Does a strong acid + conj. base create a buffer? NO
Buffer recipes 1. weak acid + conj. base 2. weak base + conj. acid 3. weak acid + strong base 4. weak base + strong acid
All acid/base rxns produce salt. T / F TRUE
Strong acid / strong base titrations are characterized by _____ graphs. sigmoidal
For strong acid and strong base,w here does rapid change occur? near E.P.
For strong / weak titrations, where does rapid change occur? at the beginning
What is Henderson - Hasselbach equation used for? to calculate pH for buffers
What does the pH of a solution depend on? strength and concentration of the reagents
Strong / weak titrations are characterized by ______. lip-o-weakeness curves
Does the E.P. for a strong acid / base ever change? NO
What are the strong acids? HI, HBr, HCl, HNO3, HClO4, HClO3, H2SO4
What are strong bases associated with? OH, NH2, H, O
ionization of water Kw = Kw = 10^-14
Formula for pH pH = -logH
What does pH for pure water = ? 7
Is CH3COONa the salt of a weak acid or base? salt of a weak acid
Is NH4Cl the salt of a weak acid or base? salt of a weak base
pKa = - log Ka
pKb = - log Kb
When acid = conj. base for a buffer, what else is equal? pH = pKa
When base = conj. base for a buffer, what else is equal? pH = 14 - pKa
pKa + pKb = 14
When solution is low pH, indicator is in which form? protonated
When solution is high pH, indicator is in which form? deprotonated
At 1/2 E.P., how much of reagent has been titrated? half
Going from a pH = 1 to pH = 2, means to go from 0.1 to? 0.01
What does a pH = 0 equal to? 1
What does a color change of a rxn depend on with an indicator? pKa of indicator
A weaker acid needs a stronger / weaker base to abstract H? stronger
A stronger acid needs a stronger/weaker base to abstract H? weaker or stronger base can work
What are strong bases? Group I / Group 2 + hydroxides
Do metal ligands act as lewis acids or bases? lewis acids
Are all Arrhenius acids and bases also BL acids and bases? yes
Generally, are hydrogens attached to carbon acidic? GENERALLY no with acids / bases
Are the hydrogens on NH4+ acidic? NH3? YES / NO
What creates an Arrhenius acid? compound can lose a hydrogen and leave behind a stable compound --> react with water to produce hydronium
Are negative ions lewis acids or bases? lewis bases
Are positive cations lewis acids or bases? lewis acids
Are all Lewis acids Bronsted-Lowry? Are all BLs lewis acids? NO / YES
What type of compounds are lewis acids? cpds with leaving groups, double/triple bond, incomplete octet
Every dilution by a factor of 10 increases pH by? 1 unit
To form a conjugate base... To form a conjugate acid... -remove hydrogen -add hydrogen
Do weak acids/bases necessarily have strong conjugates? NO
What is the definition of a strong acid? Weak acid? stronger than hydronum / weaker than hydronium
What are the strong bases from group 2? Ca, Sr, Ba
When a pH goes up by one, hydrogen ion concentration increases by? a factor of 10
Is hydride or hydroxide ion stronger base? hydride
The equilibrium for autoionization of water lies to the left/right? -left 2H2O --> H3O + OH
What is the pKa of distilled water? 15.74
What is the Kw for water? 1E-14
Equilibrium in an acid/base reaction will always lie on the weaker/stronger side? weaker
What do you need to consider with dilute solution? autoionization of water
Which cations do not form weakly acidic solutions in water? alkali metals and alkaline earth metals
amphiprotic act as acid or base
What kind of cation forms the strongest acidic solution? small and greater charge cation
At what pH is there the most rapid change in a strong acid/strong base titration? at E.P.
Does pH = 7 at the E.P. for strong/weak titrations? no
What creates weak electrolytes? compounds that do not dissociate
Does an acid dissociate more or less in more concentrated solutions? less
Does acid strength increase or decrease with increasing concentration? increase
What is a strong base? base that is stronger than OH-
Are metal hydrides basic or acidic? basic
Are nonmetal hydrides basic or acidic? acidic
For strong acids, the concentration of dissociated H+ is the same as? original concentration of the acid
What is an equivalent? mass of acid/base necessary to produce or consume one mole of protons
Does adding a small amount of water to a dilute, buffered solution effect the pH? NO
For haloacids, how to guage acidity? look at electronegativity of central atom
How to choose indicator for titration? pH (equivalence) = pKa(indicator) +/- 1
Does a more concentrated acid have a lower or higher pH? lower pH
In a BL acid/base reaction, is an H- transferred or an H+? H+
Created by: 507935299