Acids and Bases Gen Chem

Common strong acids

HI, HBr, HCl, HClO4, H2SO4, HNO3

Bronsted Lowry

Acids: Proton donors

Bases: Proton acceptors

Lewis

Acids: Electron acceptors (electrophiles)

Bases: Electron donors (nucleophiles), lone pairs or - charge

Amphoteric

Can act like an acid or a base H2O

Periodic table

BEARN

Basic, Acidic

Ka=

Products over reactants

Ka=[H3O+][A-]/[HA]

Ka>1 strong acids

Strong bases

Group 1 hydroxides like NaOH, group 1 oxides like Li2O

Weak bases: NH3

pH=

-log[H+]

Example for math

pH=-log(0.025)=-log(2.5 × 10^-2)

-log=exponent so pH=-(-2) this is the max minimum is max-1

Note bigger concentration closer to minimum

For bases

Get pOH range then convert to pH using pH=14-pOH

pOH=

pOH=-log[OH]

pH + pOH =

14

Pka=

Pka=-logKa

Low Pka=strong acids

Pka + pKb =

14

Weak acids

HCN—H+ and CN-

0.2 M 0M 0M

(0.2-x)M xM xM
x²/0.2-x = Ka

Math example for weak acids

x2/0.2-x = 6 × 10^-10

=x²/0.2=6 × 10^-10

x²=1.2 × 10^-10

square roots is exponent divided by power so -10/2 =-5

x=10^-5 so pH = 4-5

Acidic salt vs basic salt

Acidic salt:

Ignore anions focus on cations for acidic

Group 1 and 2 metals=neutral (Na etc.)

All else acidic

Basic salt:

Ignore cations, focus on anions for basic

Cl-, Br-, I- neutral

All else basic

HCl, HBr, HI all strong acids so conjugated bases are very weak (neutral)

Diprotic acids

Step wise 0.1 M

H2SO4 diprotic strong acids—H^+ and HSO4-

then HSO4—-H^+ and SO42-

After first H+ and HSO4- both 0.1 M but after second H+ more than and then HSO4 is less than because consumed again

Percent ionized

[H+] or [OH]/original M

if Pkb is 6 and Pka is 8 than bases dominate in thsi case

Henderson Hasselbalch equation

For acids: PH=pka + log ([conjugate base]/[weak acid])

Buffers

Buffering capacity concentrations that can be absorbed, if change concentration carrying capacity does not change

PH does not change with dilution since it is based on ratios!!!

PH and pKa comparisons

if pH and pKa the same then 50 % HA and 50% A-

3.5 pH and 4.5 Pka then 90% HA and 10% A-

if pH<pka the acid form dominates (pH lower so more acidic)

if pH>pka than acid deprotonated

Titration curves

For strong acid and strong bases pH=7 at equivalence point and ½ equivalence point pH=pka

For weak acid equivalence point pH>7 strong conjugate base

For weak base pH<7 strong conjugate acid

Diprotic acids have 2 equivalents points pHequiv point=average around it