AP Chemistry Unit 8

make buffers with

weak acid and salt of conjugate base or vice versa

Group I and II metal cation with anion of a weak acid:

basic

Group I or II metals cations

neutral

factors affecting acid strength

* H-A bond must be polarized w 8/S+ on H and 8/S- on A
* acid stronger when bonds weaker
* stable anion; stronger acid

determine pH of weak acid and strong base (equimolar)

from conjugate base of weak acid eq point, ICE for \[OH\], find Kb

Hydronium Ion

The H3O+ ion; a hydrated proton

7 Strong Acids

HCl, HBr, HI, HNO3, H2SO4, HClO4, HF

Strong Bases

soluble hydroxides (alkali/alkaline earth metal hydroxides)

Strong Acids and Strong Bases

completely dissociates/ionizes

pH=

\-log\[H3O+\]

pOH=

\-log\[OH-\]

\[H3O+\] represents

an acid

\[OH-\] represents

a base

pH+pOH=

14

equation for dissociation (weak acid)

Ka=(\[H3O+\]\[A-\])/\[HA\]

larger K value

stronger acid

pH from Ka method

1. chemical equation for ionization equilibrium
2. equilibrium constant expression
3. table for initial/change in/equilibrium conc (put in terms of x)
4. substitute equilibrium conc.s into constant expressions, solve for x

determine pH of strong acid and base

excess divided by reactant excess

determine pH of weak acid and strong base (weak acid in excess)

pH=pKa+log \[A-\]/\[HA\]

determine pH of weak acid and strong base (strong base in excess)

Molarity of base

determine pH of strong acid and weak base (weak base in excess)

HH equation

determine pH of strong acid and weak base (strong acid in excess)

Molarity of solution from excess hydronium ions

determine pH of strong acid and weak base (equimolar)

conjugate acid of base

determine pH of weak acid and base

will reach equilibrium

polyprotic acids

more than one acidic proton; easier to remove first proton

Binary Acids

H + 1 other element

factors of binary acids

* H-A bond most important factor
* bond polarity most important within a group
* pKa goes down, acid goes up
* electronegativity decreases; weaker bonds

oxyacids

H + O + other element

factors of oxyacids

* electronegativity of nonmetal increases acidity
* more Os, more acidic
* electron density decreases, acidity increases
* resonance structures increase, anion more stable

inductive effects

* add more electronegative atoms, acid strength increases
* increased electronegative atoms makes base weaker

carboxylic acid

contain COOH

factors of carboxylic acid

* other O-C takes from O-H and increases polarity
* conjugate base has resonance forms to stabalize anion

Nitrogenous Bases

contains N; usually properties of bases; in DNA and RNA

anions of strong acids

are neutral

anions of weak acids

are conjugate bases; produce OH- in H20

Ka>Kb for ion

anion acicdic

Kb>Ka for ion

anion basic

hydrolysis:

reaction with H2O to produce H+ or OH-

polyatomic cations

usually conjugate acid of weak base

transition and post-transition metal cations

are acidic

Group I and II metal cation w anion of strong acid:

neutral

t/pt metal cation of polyatomic cation with anion of strong acid:

acidic

t/pt cation or polyatomic cation with anion of weak acid:

greater Ka or Kb determines pH

titration

change ration of acid and conjugate base

equivalence point:

acid and conjugate base equimolar

each indicator

has own pH range for color change

buffers:

weak conjugate acid-base pair restricts drastic change in pH

optimal pH:

pH=pKa