AP Chem unit 8

Acid

Acid

A compound that donates a proton (H+ ) in a reaction (according to bronsted-Lowry

Base

A compound that accepts a proton (H+) according to bronsted-Lowry

Strong Acid, Strong base

Strong acid dissociates completely.

Strong bases ionizes completely

Weak acid, Weak base

These will establish equilibrium (do not react completely)

% ionization

The extent to which an acid or base dissociates can be found by its percent ionization.

%ionization = [A-] / [HA] * 100

For a base % ionization = [HB+]/ [B] * 100

Always just it’s conjugate over the acid or base * 100

Water is _________. Meaning it can act as a acid or a base

Amphoteric

Common strong acids

HCl, HBr, HI, HNo3, HClo4, H2SO4

Common strong bases.

.Any Group 1 or 2 hydroxides:

LiOH NaOH KOH BaOH2 SrOH2

PH,

p anything equals?

Ph scale?

Value that can tell us concentration of Acid or base.

P (anything) = - log (anything)

pH = ?

Anything in [] = concentration = moles/ L

-log [H+]

pOH=

-log [OH-]

pKa=

-log [Ka]

pKB

-log [KB]

pK w=

-log [kw]

How to convert from p(something) to concentration or to Constant? : ka kb kW etc..

If you are give the ph, simply put it as a negative exponent to ten to get concentration or constant

10^-ph = [H+]

10^-poh = [OH-]

10^ -pKa = Ka

Increasing Ph means ______ [H+]

Decreasing ph means______[H+]

Decreasing ;

Increasing

When there is High Ph, it is ________ for additional base to dissolve

Harder,

Because at high Ph there isn’t a high abundance in H+ ions make the solubility lower, because base need to react with acid to form water or else doesn’t dissolve.

Due to common ion

When there is abundance in H+ ions (low ph), the solubility of addition base would ______

Increase,

The H+ ions will react with the OH, decreasing concentration shift equilibrium to the right.

Many Hydroxide salts will _____ dissolve well in high PH

Many Acids salts will not _____ dissolve well in low Ph

This is due to common ion effect.

So acid dissolve well when there are things to neutralize not if things are already acidic

Same for base, dissolve well when things are acidic , not if already basic

For strong acids / bases, you can ______ find ____ from concentration.

strong acids goes to ________. No tendency for_______

Always; Ph

Completion; reverse

Weak acids / bases

Unlike strong, they do not dissociate all the way through, and most acid molecules remain as undissociated aqueous particles.

To solve for pH of these, sometimes Ice box is needed

X is always insignificant in weak acids

For weak acids / bases , x in ice box is?

Almost always insignificant compared to the initial concentration of the acid, so we just use the initial concentration in calculation

Acid dissociation constant

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

Always product over reactant

Base dissociation constant

Kb= [HB+] [OH] / [B]

Equilibrium ICE problems

MAKE SURE YOU CAN DO THESE

Percent dissociation (percent H break free)

Primary factor when it comes to determining acid strength depends on amount of H+ ions it can donate,

Electronegativity affects the dissociation, HIGH = LESS DISSOCIATION

EASIER FOR H TO BREAK FREE, the stronger the acid

Oxyacids ex: HCLO2,HCLO3 ,H2SO4, H2SO3

The overall all trend for oxyacids is the more oxygens that are attached to an oxyacid, the stronger it will be

Concentration’s relation with percent dissociation?

The lower the concentration is for an acid the higher the percent dissociation.

Because over abundance of water molecules makes it easier for acid to find water to donate to, and it hinders the reverse reaction, because H3O+ and conjugate base are more spread out in a dilute solution (low concentration).

Greater concentration lead to greater conjugate base

Are all hydrogen in acid dissociable?

No, because only the hydrogens that are attached to elements with very big electronegativity differences can dissociate., Ex: oxygen. not like carbon with similar diff

Can Ph effect solubility?

Yes, due to common ion effect, high ph substance have hard time dissolving in high pH, low ph substance have hard time dissolving in low ph

Polypro tic Acids Ex: H2So4, H3 Po4

Acids that can give up more than 1 hydrogen in solution.

They give up first easily than future electrons

The equilibrium Constant of water

Kw= 1.0 × 10^-14 at 25 C

This can be useful because Ka * Kb = Kw,

You can manipulate using ka to fin kb, or kb to find ka,

KW divide by either = the other k

pH + pOH=

14

pKa + pKb = ?

14

pKa, or pKb = what at half way point?

Ph at halfway point

Since kb, kw, ka are equilibrium constants, a change in temperature will?

Change their value, any equilibrium constant will experience a change in value if the temperature does.

Neutralization reactions:

Strong Acid + Strong base =?

Dissociated completely

Always RESULTS in creation of water H2O

Strong Acid + weak base

Conjugate acid of the weak base will be produced

Weak acid + strong base = ?

Conjugate base of the weak acid and water

Weak acid + weak base = ?

Simple proton transfer reaction, in which the acid gives protons to the base.

Buffer

A solution with very stable pH, that will fight stress (addition of acid or base will not greatly effect ph)

Created by adding weak acid or base WITH IT’S Conjugate

Henderson Hasselbalch equation (given) , what is it used for?

Allows us to calculate the exact Ph of a buffer

Indicators

Are weak acids which change colors in certain pH ranges due to Le Chateliers,

We use Hon to indicate an indicator. It should have range of + or - 1 to be EFFECTIVE RANGE

Larger Ka indicates?

A strong acid because more will dissociate

Larger Kb indicates

A stronger base, because high dissociation level

Equivalence point

Titration when exactly enough base has been added to neutralize all the acid (into conjugate base, only [A-]) that was initially present. pH can be 7 if both are strong, but will vary due to concentration or one is weak.

Half- way point

Enough base has been added to convert exactly half of the acid into conjugate base; here the conversation of acid is equal to the concentration of conjugate base ([HA]=[A-]), At this point ka = H +, so pKa = pH, explained in the picture

The greater the concentration of the buffer the ?

more effective it is