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UW / Chemistry / CHEM 104 / What is the difference between lewis acid and lewis base?

What is the difference between lewis acid and lewis base?

What is the difference between lewis acid and lewis base?


School: University of Wisconsin - Madison
Department: Chemistry
Course: General Chemistry II
Professor: Linda zelewski
Term: Fall 2015
Tags: Chemistry
Cost: 50
Name: Exam 3 Study Guide
Description: Here is an organized, color-coded study guide for Chemistry 104 exam 3 based off the objectives provided by the professor! It summarizes the important information that's need-to-know for the exam! Topics covered: Acids and Bases, Additional Aqueous Equilibria, and Thermodynamics.
Uploaded: 11/20/2015
11 Pages 57 Views 4 Unlocks

Noah Gerber (Rating: )

Acids & Bases

What is the difference between lewis acid and lewis base?

Relationship of Katko oka Acid ionization constant Kb base ionization constant



•ka» 1 product fovered í kw = kakol inversely related (if have constant of acid=

I Kasireacteunt fewered

lower kb ivice versa)

• Larger the Ka the stronger the acid . olf kad ko, the acid is stronger than its conjugate base - Kacky, the conjugate base is stronger than its conjugate acid oko [H3O+][A-]tbase Gen's Formula : H* + MOH - MX + H2O

How buffers work?

If you want to learn more check out How is lifespan development defined?

LHA Teacia

acid base

conjugatt bare Acid ionization constant

weak acid Expression products over reactants)

Care se vids, likvids, galvents not included) HAcoust H2O) = Hžotas) Acaq? EX) pH of 0.010 M HA is 3.38, what is ka?

What are the three types of acid-base titrations?

Hacaq) + H2Oles r H 2 otaqd & A can [H3O+]= 10-pH = 103.38 _ 4.17 x 1044 0.01 M We also discuss several other topics like When did rome being founded by romulus and remus?




ka soo x = (4.17X104)*-

0.01-4.x10-4 -1.9110

0.01-X - Bronsted Lowry Acids & Bases

Acid i proton (H+) donor Base: proton (H+) acceptor - strong acids = completely wonize - strong bases - completely conice in water (wear do not) Don't forget about the age old question of What are the difference between direct and indirect interventions?

in watter(weak do not)

- String bases: - strong acids:

| Li CH , Ba(OH),aCOH)2,S (CH), Her, Hor. Hi Corap 7) HNO3, Hoy, H2 Sou We also discuss several other topics like Who are the architects of the parthenon, 447-432 bc?

кон, NaOH - weak acids! Carboxylic acids, 5 - Weak bases:


NH3 Exi Lai boxylics - cooit group We also discuss several other topics like What is recursive method?

Amine icarbon cmpclo related to Ammonia(NH3) like:


Autoionization of water

2 H2Ore) 7 H2Otaq TOH (aq) kw = [H3O+] [ort] = 10,10-14 I water = htacceptorl base) } Amphiprotiv Don't forget about the age old question of What is markovinkov's rule?

I water = itt donor (acid) s PH

• PH= -log[H3O+ ] PH 27 Neutral

OPOH= -10g [on] ? pH+pOH = 14.00 PH > basic (take the negative log) pret acidia

• Calculating pH (weak acids/ weak bases): ice table,

find ka orky (acid i base )

find pH

Finding % lonization

% jonizations concentration ionized

initial concentration

X 100%

Polyprotic Acids o Monoprotiv (single * per molecured donated) : HF,HU

• Polyprotiv (more than I ft per molecule donated); H2SO4 , 42003. Hy POU

5 Donates - stepwise manner: H2SO4 : 1) H2SO4 H2Oca 130 HSO 4 como oka vawes decrease with each step

Acid . base acid base ay


2) HSO4 ing + H2O ce) → H2ota & SO 4 coe) .

• More difficult -remove it from Acid bay acid base - negatively charged Hisor than H2SO4 Acid Strength

•Stronger acids: - weaker bands(to break and ionize easily)

- Polar bonds - For acids in same grap, bond energies decrease => weakerbond: Stronger acid

down periodic table CHF, Hu, H8v HI) - For acids in same period, electronegativity increase = more polar..

across periodic tabie bond storage acid

Oxoacids, H-O- bond (HNO3. HUOM! H2 504)

- acid strength decreases with deireawing electronegativity of group attached to o



ka: 66.88108 2.5x10-9 a 2.3x10

Equilibrium of ran

favors weaker acid & base - ka valve increases for each additional o ator


HClO4 Kai 6.8x10-8 108 o carboxylic acids; -COOH

1 -acid strength increases with addition of electroneg, atom



Acetic Acid

chloroacetic Acid Ka: 1.8x105

2x 10-1 Acidic & Basic Oxides

- Acidic oxides Usually nonmetal oxides Oreciter electroneg. of atom other than o a Greater oxidation # of = stronger acid

ve Most acidic oxides - upper right of periodictable

Basic Oxides usually metai oxides

Most basic oxides lower left of potable

CO2(g) + H2Our H2CO3 caq) Adic oxide

I Diprotic Acids: Kask be kw

Ком К. : [w

Diprotic Acid

4 H2CO3 (4) + H2O u ħ HCO3 cae) + H2Otcan) kao = 4.3x10-7 MfOg lagd + H2OC) F (Ozaron + H307aa) Kaze = 4.7x10""


- conj.base: can accept the s...)

y Acid Amphipnotic base COZ) + H2Ore) HCO3 cod TOH cug) Kbi = 2.1 X 1024

HCO3.com) + H2063 B H2COg lag) + oH cng Kbz = 4.7x10-" ) Acid-Base Rxns of Salts

• Strong base & strong acid = hectral salt

Ex: HCI caq) + NaOH(aq) → Naci (@as + H2Ou) overall eqn ? no significant

H30 Fram) + OH can) ->

( amounts of ands H2Oce) + H2O w

Not innic ecn

Net ionic eqin ) or bases Acid base

base acid

• Strong base + weak acid basic salt

Ex: CH3COOH called + NAOH → NaCH3C00cc ad + H2O(l) Hydrolysis: water meewie

Produced from split bin aid+ weak base + strong acid acidic salt

EX: NHz (aq) + HCicace) → NHU Clcaq) + H2O(l) o weak bass & weak acid acidic or basic (must look at ka and ko vawes which one is bigger) Lewis Acids & Bases

lewis Acidi accept e- ppair coordinate covalent bond: An e-pair bond in which both lewis base donate e pair s e-s il me from one of the bonded atoms

H+ + H2O +Bot nop's a lone pairs complex ion metal ion bonded to one imore leuis bases

by coordinate covalent binds-form complexion

[Fe (H2O).]* )



ocations netrall-group's IA + Ba(metal)

I Anions

conjugare bases of I strong ands


Acidic - Nhyt A13+

T-conjugate acids of aminus/-some amphiphotic

amions - Transition metui ions I (compare kaikil Basic


|- Conjugate buses of

weak acids - Some amphiprotic unions(compare Kat kb)



o Buffers: Solution-resists changes in pit when dimited amounts of audl base are added

- consists of weak acid & conjugate base

uporabo rossobu obogonupasaud PH of water changes a lot wi strong base lacid

pH of latter hardly changes Ex. HC. 2+1302 and Nalzt30. = buffer

Acetic Acid Acetate

(The weaker the acid, the larger a NH.3 and NHyCl = buffer

Aska & pka? its oka) Calculating PH of buffer

• If biffer + ice table or Henderson Hapselbaich eant pH=pkat log THAT opti of solution that is

Xaiways try to wl buffer?

rings 0.25 NHC2H302 and 0.25 M NaC, H.302 !

PH=pka + log mola

NOHA Ka = 1.8x10-5

C Buffer! ICE weak Aud

Henderson Hapselbaich HA(aq) + H2011) S Acaq) +H30124) ) 1) 0.25 M - 0-25M 0

DH = 4.74 +

loa [A


Coni base

pka = -log(1.8x105)-4.74



pH = 4.74 +10910:25) -(4.74









proximation study soup

1.8x105. X(0.25+X)

& Maks.

Approximation 1.8x10-5= X(OAS)

om → [H30+]=1.8x10-5

Find best conj. acid-base pH= -log(1.8x10s) = 14.74

pair to prepare buffer o want the pH=pka "Buffer range: pH=pkati Ex: Which conj. aud/base pair should be used to make a buffer with a Hydronium ion

Concentration of 5.ox 10-4 M?

A) HF + NaF, pka (HF) = 3.19 How Buffers work

I Coul pH

olf strong wid is added to buffer, it reacts with the weak buse weak acid olf strong base is added to buffer, it reacts with the weak acid weak base

pH = -log (5.0*10-4 M) = 3.3



Buffer after acid

Buffer wi equal amounts

conjugate acid thase

Buffer after base

Study SOU



reverse, so





Strong base added ФК НС „Н,0 сая тон сая) гCHз о, сая) + H2O Ce) -

wear acid Strong base weak buse

reverse 4 C2H30, lagi +How ? H (H 30, + oH Kb Strong Acid added - C2H30 caa) + H30tcaad HC 2H3Ozcan) + H20 (1) -

+ HH40сещ) +Hote)-H40*cae) + Сң, сау ұo Calculating pH as ren changes Ex. what is pH after adding 10mL IOM NaOH to stomL of buffer so in that

15 0.25 M HC2H302 & 0.25M NaC2 H2O2 ?

- String (0-25 mol HA ) ( .500 L) = 0.125 mol HA HA TOH

+ H2O

I start 1.125 mol .010 moi o 125 noi (0.25 molA-) (.500 2) = 0.125 mol A

( change|-1010 010 toto (1.O mol OH)(0.1001) = 0010 moi on) Finai 10.115 mei o plss =


PH zpka + log molt

Buffer Capacity &

pH=4.74 + log (175) *4.83 color indicators

ApH = 4.83 -4.74 = 0.09 APH]

• Buffer capacity amount of strong acid/base a buffer can take in who changing

more than Ipt whit.

- Greatest when: 1) pH=pka 2) concentrations of acid & cong base=high

• Acid-base indicators chaneje over range pka Il - Acid-Base Titration

HAL44) + NaOHca) NaOca4) + POce) . •Nach titrant (soln in buret

Ht caq) + OHami - HyOce) (Net ionic ean) Equivalence point: point in titration

• 3 types of Acid-base titrations:

Where the stoichiometric amont of

titrant has been added cmores acido moves base)





thatkin Bromythopen





+ Equiv.pt.

Methyl initial pri




voi, NaOH (dc A. Strong Acid + strong base

Voi, Ha added




- weak base + strong Acid



ті по

total volume

Calculating pH at various pts. in Titration curve

Strong Acid + Strong base} A 0.100 M NaOH soin is used to titrate 50.0 mL of 0.100 M HC. Caiuiate pH at 4 prs (a-d) a) Before any titrant is added (v=0 me.)

H.3ot (aq) + otcaq) H2O(R)] - Only Ha present : PH = -log[.100 m] = 0 b) After addition of 40,0 m2 titrant (OC Vote)

Hot + OHH2Oce) .05 LX 10 MHCL = .005 moluch 1.005 moi.oimoi

004LX.IOM NaOH..004 molon) c .04

-2004 Flool moi o

09 Lutotal volume 4 ,001 moi

me sooL = 1.11860-2M + pH = -log4.11X60-2)-1951 total volume - ORL

+ PH C)After addition of 50 mL titrant (equivalence pt.) (Vb-Ve)

• At equivalence: mol HCl = mol Naoh and He + NacH neutral salt

catering) (string base) d)After addition of 50,2mL titrant (b>ve)

pH = 7 Excess NAOH

H3otcoad + oHiggo hoce) .0502 L xolm NaOH = 50,00502 mol S1.005 moi 00502 moi

C .005


00002 moi

4.00CO2 moi 2.00002 mol = 2 X10 4m NaOH.


pOH = -log(2x10-4)= 3.7 pH = 14-3.

8 10.3 Surak Acid wy strong bases

• Titrate somb of 0.050 Mburanoic acid CHA) with 0.10 M NAOH a) Before any tittrant is added (16=0 mi)

| HA+H AT H2Owl I weak Acid problem. ICE table

KaCHA).-1.52 X1005 find pH

Ky(A-) = 6.58 X10-10 b) Aften addition of 10 mL Hitraint CoLV L Ve)

SCF table (do rxn, then assess)

ho Buffer (weak acid and conj. base present)

ho Henderson - Hapsalbach egn

4 At Ève , CHA ) = ((so pH = pka + log() + pH=pka) c) After addition of 9o 25 me titrant. (Vozte)

y moves HA= moles OH I wear base problem Call of weak acid has been conve

4 SCF(to establish it's a weak buse problem Cice table))

LICE table(find M of A-)

4 Kb = [HA][OH-] FOOH + PH

CA-] d when Vodve: Addition of 30 ml

V6 = 30mL Ve= 25 mL

5 mL excess [OH-Iexcess = (0,10M)

i to mi toran) = ,00625 M NAOH + POH 50 ml + 30m2 tot

+ PH

sweak base + Strong Acid?

• Titrate somL of 0.10 M Nttz wl 0.10 MHE KACNrut) = 5.56x10-10

| NH4 + Hao" – NH4++ H2Oe) | L, (NH4) = 1.8 x 10^ a) Va=0mL (weak base problem)

I weak base problem: ICE Table (SCF first to establish weak base problem)

LICE table

4 kopoti #pH b) OL VALVE ( Bufffer)

- a Buffer: Henderson egin (Attiv. [NH3] = [Nryt]

4 pH = pka (NH4t) pH c) Varve (weak acid problem)

I weak acid problem: ICE table (SCF first to establish a weak acid problem)

4 ICE table

o 4 ka PH d) Va> ve lexcess Strong acid)

Va = 600 mLHO Ve=50m2

[1-12071excess = (0.10m) (080p boot roten ) = .00909 M to pH

K Excess



Effect of


Acid strength on Titration weak and strong base

ka = 10-10

Ka = 10-1


Ka = 10-4



strong acid



Volume of 1.om NaOH added

Solubility o soubility: amount of salute per unit volume of sol'n (mol/l) that dissolves to form saturated soin. okse (soubility product constant) : equilibrium bin solid ionic sowte t its ions in solh.

Ex: Cacomio F la cara) + Concaq( soubility of CaCO3 = 5.29 X 105 mol Caloz).

Ksp = [caz+] [6032]

[ca2+] = 5.29 x10-5 Ksp :(5.29X10-5)(5.29x1095): [co?]5.29x10-5


• When salts = same cation to anion ratio,

Solubility to compare *sp vawesClarger ksp=greater solubility)

• insouble salts wl basic anion = dissolve in acidic solutions (greater solubility wiacids

than water) Ex: CaCO3(s) Catrag + co2 caq)

more solebie in strong acid than pure water reacts wl Ht to form HCO3.

reducing conc. of cog2- and shifts to product side (souble)

• Common on effect. The presence of a second solute - provides common in lowers

- the solubility of ionic cmpd. Pb I (5) P62 caq) + 2I cace) 7 Pbl in accord kl = more I on product- side KI cale) K+ + I

J So equilibrium will shift to left (less




•DH = H final - Hinitial =qp

I Heat transferred bln system State function

suroundings at constant pressure


• Arlos E Coefficient of product x Of H (product)) - [[coeffic reactant x Af H'reactanr)] Enthalpy ofren

Enthalpy of formation : AH for formation - linole of

compond/substance from consituent elements in their a Ahso endothermic

Standard States. AHKO exothermic Entropy: Probability of Dispersal o Energy Spreads out Cdisperses) unless hindered from doing so (product-favored ryns) . Most exothermic rand= product favored

• Entropy i measurement of energy dispersal Cstate function)

• AS = Stinal - Sinitial o Third Law of dynamics; entropy of pure,cny stailine soubestance at OK 20

- Gas- highest entropy (most freedom of motion

really cold decreased - Solid < liquid gas


• Standard molar entropy of substance at T (temp.) is sum of quantities of energive

that must be dispersed in that substance at successive tempis up to T lov )

Guidelines for Entropy

• entropies of solids< liquid < gas

single bonds double hands

• entropies of complex molecies = larger than simpler moleculesenza

molecule (CH3 CH2 CH3> ca)

• entropies of ionic solids wi similar formulas = larger when attractions -

among ions are weaker (easier for ions -vibrate)"

NaF Mgo 51.5JK mor- 26.94

r 2 units of charge = stronger = (smalier entropy) Nat F

Mg 2+ o2-k

NaF 51.5

Nacl< chloride ions = larger than F-ions, weaker/ farther 72.13

apart = larger entropy

• Entropy decreases when gas dissolves in liquid calculating entrepy

Ars = [coeffic. prodiet x 5°Cproduct)]-[[coeffic, of reacteint x Sorreactanr)]


o second law of Thermodynamics

- Total entropy of universe (system + surandings) = continually

As universe = AS system & Assurandings! - If As universe so product favored (if also exothermic)

As universe to reactant-pavored (if also enclothermic) – For Temperature-constant process:


A Scorureling = SH 39 = -Hayson = -6FH





E1: 2 NO cg) + O2(g) + 2NO, (g)

Arte = (z moi No, )(33.18 kJismos ) - [C2 mot No) (90.25 kb/201)+(I mon) (OKS)gas) Arho = -114.14K) Assum. = +114,140

zase = 383 V + Asiniverse = -146. 14x + 383 x = 236 Gibbs free Energy

favored I AG system - At system = TAS sys!


-Tar Suniverse, so if entropy of universe 1, Gibbs free energy (blc of minos sign):

• Decrease in Gibbs free energy of systern= product-favored rxn

• AGO <0 product-favored a Ago do reactant- favored

lfrxn is exothermic: Art is negative => favors products -If products = greater entropy than reactants, Drso is positive and

-Tars' is negative => favors products. DH and AS° do not change much wi temperature ( if substances in same

State of matter EX: At what temp. is ron below product - favored?

Art=403.7K) Casoy (s) (ao(s) + S02L9)

Arso = 188.50k AG = Gfinal- Ginitial .

T: 403100 312142 K AG=[coeff. product x A of product]

-Licelf reactant X AGP Creactares ]



188.5 JIC

• AG : max. amount of work-can be done by product - favored on

' (min. amount of work-force reactant - favored run)

ridical Cous constant (8.314 %kmai)

At equilibrium

under standard state NGO and Q=K TAG-AG + RTenQk rxn quotient conditions non-standard Standard

o=D6°+ Renk


TAG" = -Rrenkl Tk=en


Statt conditions

State Conditions

Strong acid &

weak acid a


voi. Nu CH added




Cheat Sheet


oKw=kako Kw = [+.30+][OH-]= 1.0810-14

Acid-Base Titrations

• Ka >>i: product - favored


Kaal: reactant-favored

• Equivalence pri mores acid=moes base


Kalkb2= kw

weak base &

• Stronger acid = larger Ka

Strony base

Strong base strong acia

Kaz Kbi = kw

o ka = [H3O+][A-]<base

THAJ & acid

Acids Bases

•PH a throughout titration curve (weak aid base)


1) volva Oml (weak ucid I weak baise problem)-ICE +PH

a proton CH+) donor (Bronst. Loury) oproton acceptor e-pair acceptor Clewis)

2)0yolva Vecbuffer) + SCF + Henderson-ean pH

el pair donor

12 Ver [HA-[A]

•Strong acids: HU, HBr Hi Strong bases: Barolt)2, Cacom)ą, SP COH), / 3) Vol va = Ve (weak base l weak acid) + ICE + OH Нез нСоч , H4

KOH, Licho, NaOH weak acids: Carboxylic Acids, weak bases: NH3r

il Vind Va sve (excess): [OH] or [H204] =(M) ( mlekces)


3 Solubility

• Ksp = [Ca 2+ ][co,2-1 (su lub. CaCO3 =5.29x10*5 mol new MpH

• Strong bast & strong Auid =neutral sait Strong base + weak Acid: basic sait

Ksp = (5.29x10-5)2 +2.8x10-9

weak base to Strong Acid = acidic sait weak base to weak acid= acidic or basic


(compare kat Kovalves)

AH o endothermic

s)) AH = Hindi - Hinitial = 9p AHCO exothermic


Arho=E[coeff. product of hl product) ] - [cceff. react. x DfHicreacton)]

PH Of Buffer + Henderson - Hapsalibacheqin 0 PH=pka + log [A- ] or harra

/ Entropy

THAT or pHapka + loq moi A or TCE Table I molHA

As = Sfinal - Sinitial

• Best conj. acid-base pair for buffer: Caso a favored Arso=E[coeft.product * Scproduct)]-{[ceff.react. * SoCreactant)] pH=pka ar range pH=pica #1

texothermit | Asuniv. <O reactant- favored

Seniverse = A'S system + AS serrandings

• Strong acid + buffer weak acid/ Strong base + buffer weak base 1 Gibbs free thergy

At equilibrium Standard State conditions Absystem = At sys. -TAS sys. DG <0 product favored AG=AG"+RT enQ

5 so +

+ Toon

A6 = 46° + RI enco


Q=17AG-AG Ar G* -- [coeff. prod. X AGF '(proces)] - Ercefr. reactant. x DGf"Creact.) ] -

AG's-Rienk Kee RT

lendothermic) Assura = -Ar Ho

AG to reactant favored

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