Chapter 18 Acid-Base Equilibria / Gen Chem 2

what are the three common acid-base definitions

Arrhenius, Bronsted-Lowry, and Lewis

acid

substance with H in the formula that dissociate in H_2O to yield H_3O^+

Base

substance with an OH in formula that dissociates in H_2O to yield OH^-

neutralization reaction

reaction of strong acid and strong base that yields salt + H_2O

strong acids / bases

complete dissociation or complete conversion into ions in H_2O

a dilute solution of a strong acids contains no HA molecules

weak acids / bases

dissociate only partly in water or incomplete dissociation

a weak acid dissociates slightly to form ions in water

in a dilute solution of a weak acid, most HA molecules are dissociated

what is the acid dissociation constant

K_a

measure of the strength of an acid

the stronger the acid, the higher the [H_3O^+}, the larger the K_a

the weaker the acid, lower the % of dissociation of HA, the smaller the K_a

general reaction of derivation of K_a

HA(aq)+ H_2O(l) → A^-(aq)+H_3O^+(aq) where H_2O is treated as a constant

nitric acid

SA

HNO_3

sulfuric acid

SA

H_2 SO_4

Hydrochloric acid

SA

HCL

Hydrobromic acid

SA
HBr

Hydroiodic acid

SA

HI

perchloric acid

SA

HCLO_4

hydrofluoric acid

WA

HF

Phosphoric acid

WA

H_3 PO_4

Carbonic acid

WA

H_2 CO_3

Sulfurous acid

WA

H_2 SO_3

nitrous acid

WA

HNO_2

hydrogen sulfide or hydrosulfuric acid

WA

H_2S

hydrogen cyanide or hydrocyanic acid

WA

HCN

organic acids

WA

formic acid - HCOOH

acetic acid - CH_3 COOH

lithium hydroxide

SB

LiOH

Sodium hydroxide

SB

NaOH

Potassium hydroxide

SB

KOH

rubidium hydroxide

SB

RbOH

Cesium hydroxide

SB

CsOH

calcium hydroxide

SB

Ca(OH)_2

Strontium hydroxide

SB

Sr(OH)_2

Barium hydroxide

SB

Ba(OH)_2

ammonia

WB

NH_3

organic amines

WB

strong acids

O>(O-H)+2

weak acids

H not bonded to O or halogen

O=(O-H) or (O-H)+1

pH scale

both H_3O^+ and OH^- are always present in (aq) solutions ( both are 1 × 10^-7)

K_w= 1.0 × 10 ^-14 at 25 degrees C

in acidic solution

H_3O^+ > OH^-

pH < 7

in basic solution

H_3O^+ < OH^-

pH > 7

in neutral solution

H_3O^+ = OH^-

pH= 7.0

as H_3o^+ conc increases

pH decreases and vise versa

pK_a

a way of expressing K_a without exponential notation

low pK_a , higher K_a, stronger acid

negative pK_a, stronger acid

bronsted lowry acid

an acid is a H^+ donor

all Arrhenius acids are BL acids and vice versa

a BL acid donates a H^+ to H_2O

Bronsted Lowry base

a base is a H^+ acceptor

a base need not to be an OH compound as in Arrhenius

a base must contain a lone pair to binf H^+

a base accepts a H^+ from H_2O

Conjugate acid-base pairs

acid - will produce a base product and the two will establish an acid-base pair where the conjugate base of an acid has one fewer H^+ and one more (-) charge

base - will produce an acid product and the two will establish an acid-base pair where the acid of a base has one more H^+ and one fewer (-) charge

conjugate pairs

the net direction of an acid-base reaction depends on the relative strength of the acids and bases involved

acid-base reactions proceed to give the weakest acid/base

if the acid is above the base on the list, it will proceed right

base dissociation constant

K_b

a measure of the strength of a base

base doesn’t dissociate

ions are produced upon reaction with water

larger the K_b the stronger the base

polyprotic acids

acids with more than one ionizable proton

the dissociation of the first H^+ is easier than the second, which is easier than the 3rd

K_a1 > K_a2 > K_a3

the strenght of an acid id dependent on what?

its ability to donate its bonded H^+

what are the two factors that the dissociation of HA is influenced by?

1) strength of HA bond ( the stronger the H-A bond, the weaker the acid

2) the H-A bond polarity ( the greater the bond polarity, the stronger the acid)

group 16 and 17 hydrides acid strength depends on what?

the EN of the central nonmetal

the strength of the E-H bond

down the group and across the group the acid strength increases

oxoacids in which the number of O atoms exceeds by 2 or more

the number of ionizable protons are strong

oxoacids in which the number of O atoms equals or exceeds by 1

the number of ionizable protons are weak

hydrated metal ions

ability to transfer an H^+ to H_2O and form acidic solutions as a result

most are weak acids

if its a small ion and highly charged, it will withdraw enough electronegative density form the O-H bonds of the bound water molecules to release H^+

salts that yield neutral solutions have both

conjugate acid of a strong base = cation of a strong base

conjugate base of a strong acid = the anion of a strong acid