Acids and Bases (Chem I + Chem HL II)

a substance that contains hydrogen and ionizes to produce hydrogen ions in an aqueous solution.

Arrhenius definition of an acid:

a substance that contains a hydroxide group, and, when dissociated in water, yields hydroxide ions.

Arrhenius definition of a base:

properties of an acid:

- sour taste
- produces stinging sensation on skin
- reacts with certain metals to produce hydrogen gas
- reacts with limestone (CaCO3) and baking soda to produce CO2
- turns blue litmus paper red

properties of a base:

- bitter taste
- feels slippery on skin
- reacts with acids to produce salt and water (neutralization reaction)
- turns red litmus paper blue

common acids

hydrochloric acid (HCl), sulfuric acid (H2SO4), acetic/ethanoic acid (CH3COOH), nitric acid (HNO3)

common bases

ammonium hydroxide (NH4OH), sodium hydroxide (NaOH), magnesium hydroxide (Mg(OH)2)

pH

the negative logarithm of the hydrogen/hydronium ion concentration

pH=-log[H+]

formula for pH (H+)

pH=-log[H3O+]

formula for pH (H3O+)

10^-pH

[H+] = ? or [H3O+] = ?

0 to 14

pH scale ranges from

acidic, larger

the more acidic a solution is, the _________ (larger, smaller) the concentration of H+ ions.

10^x

An increase or decrease of one pH unit x means an increase in [H+] of

poH

the negative logarithm of the hydroxide ion concentration

pOH = -log[OH-]

formula for poH:

10^-poH

[OH-] =

14

pH + pOH =

A proton donor

Bronsted-Lowry acid:

A proton acceptor

Bronsted-Lowry base

conjugate acid-base pair

two substances that are related by the loss or gain of a single hydrogen ion

Change "ate" (in polyatomic ion) to "ic" and end with "acid"

how to name an acid that consists of hydrogen and a polyatomic ion

add prefix "hydro," change ending to "ic," and add "acid"

how to name an acid that consists of hydrogen in an element

name the cation, name the anion, change the suffix to '-ide,' or use the polyatomic anion name.

how to name a base/ionic compound

Strong acids

acids that dissociate completely in water and are therefore strong electrolytes

electrolyte

a solution that conducts electricity

examples of strong acids:

HCl, HBr, HI, H2SO4, HNO3, HClO4

weak acid

acids that ionize or dissociate partially in water, and therefore are poor electrolytes

reversible

partial dissociations/reactions with weak acids or bases will always be ____________

strong bases

bases that dissociate completely into metal ions and hydroxide ions. also strong electrolytes

examples of strong bases

NaOH, KOH

weak base

bases that dissociate partially in dilute aqueous solutions. also weak electrolytes

autoionization

the transfer of a proton from one molecule to another of the same substance. (In a sample of pure water, a very small number of water molecules ionizes, producing equal concentration of both hydrogen and hydroxide ions.)

Neutralization

a rxn in which an acid and a base react in an aqueous solution to produce sale and water. DOUBLE REPLACEMENT rxn.

acid-base titration

a method for determining the concentration of a solution by reacting a known volume of the solution with a solution of unknown concentration.

lone pair acceptor

lewis acid

lone pair donor

Lewis base

nucleophile

an electron-rich species that donates a lone pair to form a covalent bond in a reaction. another term for an electron pair donor or lewis base

examples of nucleophiles

OH-, NH3, Cl-

electrophile

an electron-deficient species that accepts a lone pair from another reactant to form a new covalent bond. another term for electron pair acceptor or lewis acid

examples of electrophiles

BF3, CU(2+), Br+, NO2(+)

Coordinate bond

the shared pair of electrons that come from the lewis base.

kw

ionic product for water

1x10^-14

at 25C or 298K, kw =

endothermic

The dissociation of water is ___________.

increases

kw value ____________ (increases, decreases, stays the same) with an increase in temperature.

Ka

acid dissociation constant

kb

base dissociation constant

strength of acid

as ka increases, what also increases?

strength of base

as kb increases, what also increases?

negligible

if ka or kb is less than 10^-3, dissociation is considered ________________. in other words, initial [acid/base] = equilibrium [acid/base]

pKa = -logKa

formula of pka

pKb = -logKb

formula for pkb

Ka = 10^-pKa

ka formula in terms of pka

Kb = 10^-pKb

kb formula in terms of pkb

inversely

ka/kb and pka/pkb (respectively) are ___________ related.

Kw = Ka x Kb

kw formula in terms of ka and kb

pKw = pKa + pKb = 14

pkw formula

buffer solutions

solutions that resist change in their pH when limited amounts of acid or base are added

Composition of an acid buffer

aqueous solution of weak acid + salt of strong base

The H+ ions combine with the base, therefore removing most of the acid.

How do acid buffers respond to added acid?

the OH- ions combine with the acid, therefore removing most of the base.

How do acid buffers respond to added base?

Composition of basic buffer

aqueous solution of weak base + strong acid

- start with an acid or base with a pKa or pKb value as close as possible to the required pH of the buffer
- mix in either (a) a solution containing a salt and its conjugate or (b) partially neutralized by a strong acid or strong base
- after the reaction mixture will contain unreacted acid or base in an equimolar amount

How to make a buffer solution

No; no effect on pH, just increased volume

Does dilution affect buffer solutions?

Yes; buffer solutions must be kept at certain temperatures

Does temperature change affect buffer solutions?

salt hydrolysis

the process by which salt reacts with water. the ions contained in salt can act as acids or bases in aqueous solution

cations, anions

in salt hydrolysis, _______ act as acids and __________ act as bases.

True

Strong acids/bases do NOT undergo hydrolysis (true/false).

Titration curve: strong acid and strong base

Titration curve: weak acid and strong base

Titration curve: strong acid and weak base

Titration curve: weak acid and weak base

equivalence point

the point at which the two solutions used in a titration are present in chemically equivalent amounts

half equivalence point

The point in a titration at which exactly half the molar equivalence of reactant is consumed by the titrant being added. At this point in an acid-base titration, the pKa of the unknown solution is revealed. pH = pKa

Indicator

A compound that changes color in the presence of an acid or a base.

carbonic acid

A weak acid formed naturally when rain falls and absorbs carbon dioxide in the atmosphere.

5.6

acid rain has a pH less than ______.

sulfurous acid

H2SO3

sulfuric acid

H2SO4

nitrous acid

HNO2

nitric acid

HNO3

natural causes of SO2

volcanic eruptions

anthropogenic causes of SO2

sulfur-containing fuels, smelting of sulfide ore

S + O2 -> SO2; SO2 + H2O -> H2SO3

chemical reaction for the formation of sulfurous acid; chemical reaction for the formation of acid rain from sulfurous acid

2SO2 + O2 -> (UV light) 2SO3; SO3 + H2O -> H2SO4

chemical reaction for the formation of sulfuric acid; chemical reaction for the formation of acid rain from sulfuric acid

natural causes of nitrogen oxides

lightning, actions of some bacteria

anthropogenic causes of nitrogen oxides

internal combustion engines and jets

N2 + O2 -> 2NO; 2NO + H2O + O2 -> 4HNO2

chemical reaction for the formation of nitrous acid; chemical reaction for the formation of acid rain from nitrous acid

NO + O2 -> 2NO2; 2NO2 + H2O -> HNO3 + HNO2

chemical reaction for the formation of 2NO2; chemical reaction for the formation of acid rain from nitrous AND nitric acid

4NO + 2H2O + O2 -> 4HNO3

chemical reaction for the formation of acid rain from nitric acid

- affects statues or buildings made out of limestone and marble
- kills fish and other forms of aquatic life
- increases the risk of respiratory illness in humans

Effects of acid rain:

CaCO3

calcium carbonate / limestone / marble

CaCO3 + H2SO3 -> CaSO4 + CO2 + H2O

CHEMICAL equation for the degradation of limestone/marble because of acid rain

CO3(2-) + 2H(+) -> CO2 + H2O

IONIC equation for the degradation of limestone/marble because of acid rain

- carpooling
- public transport
- hydro sulfurization
- floatation method for coal

pre-combustion methods of reduction for sulfur oxides

scrubbing method (desulfurization)

post-combustion method of reduction for sulfur oxides

CaO + SO2 -> CaSO3

chemical equation for desulfurization