acid base week 1 sec 3

acid

proton donor (H+ ion) and forms its conjugate base

base

proton acceptor and forms its conjugate acid

bronsted-lowry acid/base must contain

H in its formula/lone pair of electrons to bond to H+

each side of acid/base reaction has

an acid and a base

acid-base reaction transfers

protons

arrhenius theory

acids dissociate in water to form H₃0+, bases dissociate in water to form OH-

acid ionization

proton exchange reaction between an acid (donating proton) and water

base ionization

proton exchange reaction between a base (accepts proton) and water

water is amphiprotic, meaning

can react as either an acid or a base

conjugate acid/base pairs differ by

an H+

autoionization of water

reaction where water is gaining and losing a proton by itself, with associated equilibrium constant K_w

K_w =

[H₃o+][OH-]

if we disturb equilibria by adding base or acid

system responds i.e. increase in [H₃O+] results in decrease of [OH]- and vice versa

acidic solution

[H₃O+] > [OH-] and pH < 7

neutral solution

[H₃O+] = [OH-] and pH = 7

basic solution

[H₃O+] < [OH-] and pH >7

whether an aqueous solution is acidic or basic depends on

relative concentrations of the ions (both are present)

if equilibrium constant K for acid-base reaction is » 1

forward reaction favoring the products s.t. most of the acid HA will ionize to form A- and most of the base B will ionize to form HB+

we compare acids and bases’s strength with

eq constant of the proton-exchange reaction of the acid/base with water

acidic strength

if eq constant is very large, stronger than water and vice versa

acid dissociation constant K_a

products/reactants i.e. [H₃O+][A-]/[HA]

strong acid

K_a is irrelevant, no equilibria s.t. there is no HA remaining, complete dissociation into atoms

all strong acids are

equally strong in water

strong acids

HClO₄, HCl, HBr, HI, HNO₃, H₂SO₄

perchloric acid

HClO₄

hydrochloric acid

HCl

hydrobromic acid

HBr

hydroiodic acid

HI

nitric acid

HNO₃

sulfuric acid

H₂SO₄

weak acids leave

a measurable amount of HA at equilibrium, with the value of K_a indicating acid strength

low pK_a corresponds to

high K_a and a stronger acid

basic strength

if eq constant is very large, stronger than water and vice versa

K_b, base ionization constant

[BH+][OH-]/[B]

strong base

completely ionizes to produce OH-

lithium hydroxide

LiOH

sodium hydroxide

NaOH

potassium hydroxide

KOH

calcium hydroxide

Ca(OH)₂

strontium hydroxide

Sr(OH)₂

barium hydroxide

Ba(OH)₂

K_a x K_b =

k_w

the stronger the acid is

the weaker its conjugate base

dilute strong acid

concentration is less than 10^-6 M, so we also have to account for the water donating [OH-] or [H₃O+]

polyprotic acid

has more than one ionizable proton s.t. in solution, each dissociation step has a different K_a value

for nonmetal hydrides, acid strength depends on

electronegativity of the central nonmetal and the bond strength

across a period or down a group, acid strength

increases (due to e-negativity increase and bond strength decrease, resp.)

oxo acids

oxygen between the nonmetal and H, their acid strength depends on e negativity and number of O atoms around central nonmetal

more electronegative atom bound to oxygen

higher acidity

oxoacids with same central atom comparison

more oxygen means higher acid strength

group 1 cations have

no acidic/basic properties

for concentrated solution of weak acid, [AH] » k_a

[H₃O+] = √[HA]_initialK_a

for concentrated solution of weak base, [B] » k_b

[OH-] = √[BOH]_initialK_b