Chapt. 16 Acids and Bases (1)

7/28/2019 Chapt. 16 Acids and Bases (1)

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SAVE PAPER AND INK!!! Whenyou print out the notes on

PowerPoint, print "Handouts"instead of "Slides" in the print setup.

Also, turn off the backgrounds(Tools>Options>Print>UNcheck

"Background Printing")!


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16.1 The Oldest Theory is the Arrhenius Theory


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Arrhenius looked at the substances which were calledacids

taste sourturn blue litmus to red

neutralize bases

release hydrogen gas when added to an active metal

release carbon dioxide when added to a carbonate.
http://innovations.oise.utoronto.ca/science/index.php/Image:Volcanoerupt.jpghttp://innovations.oise.utoronto.ca/science/index.php/Image:Volcanoerupt.jpg


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and said these properties were due to the productionof H+ ions when acids dissolve in water.


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Today we know that a bare proton does not exist inwater, it forms a chemical bond with a water molecule

forming the H3O+

. This ion is called the hydronium ion.


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Arrhenius looked at the properties of bases.

taste bitter

feel slippery (soapy)

turn red litmus blue

neutralize acids.


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Arrhenius said these properties were due to theproduction of OH- ions when bases are dissolvedin water.


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NaOH sodium hydroxide lye

KOH potassium hydroxide liquid soap

Ba(OH)2 barium hydroxide stabilizer for plastics

Mg(OH)2magnesium hydroxide MOM Milk of

magnesia

Al(OH)3 aluminum hydroxide Maalox (antacid)


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Arrhenius acid is a substance that produces H+ (H3O+)

in water

Arrhenius base is a substance that produces OH-in water


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Neutralization is

H+ + OH-H2Oor TODAY

H3O+ + OH- 2 H2O


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This acid base theory is limited to water solutions.WATER must be the __________.solvent


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Another Acid/Base Definition

Brnsted - Lowry Theory

acid donates a proton in a proton transfer reaction.

What is meant by a proton here? A proton is reallyjust a hydrogen atomthat has lost itselectron!


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B/L base is the species which _________ .

general acid - base reaction:

HA(aq) + B(aq) HB+

(aq) + A-(aq)

acid base conjugate acid conjugate base

Accepts a proton

j


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conjugateadj \kn-ji-gt, -j-gt\Definition of CONJUGATE1

a: joined together especially in pairs :coupledb: acting oroperating as if joined2

a: having features in common butopposite or inverse in some particularb: relating to or being conjugatecomplex numbers 3of an acid or base: related by thedifference of a proton


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A Brnsted-Lowryacidis a proton donor

A Brnsted-Lowrybaseis a proton acceptor

acid conjugatebase

base conjugateacid


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HClO4 perchloric acid

HI hydroiodic acid

HBr hydrobromic acid

HCl hydrochloric acid

H2SO4 sulfuric acid

HNO3 nitric acidWhy do we call them strong acids?

- They ionize 100%...Ka is large

H2SO4 is special because it is diprotic. There is an equilibrium constant for theremoval of the 2nd H+.

C j t b


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Every Brnsted - Lowry acid has a _________________,and every B/L base has a _______________

For a specific weak acid reaction:

With a weak acid, we have an equilibrium mixture of allfour species. Weak acids do NOT dissociate 100%.

Conjugate base

Conjugate acid


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CH3COOH is the _____________________.

H2O is the _________________________.

H3

O+ is the ____________________.

CH3COO- is the _____________________.

acid

base

Conugate acid

Conjugate base


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For a specific weak base reaction:

OH- is the ____________________.

NH4+ is the _____________________.

NH3 is a weak base. There are not many ions in

solution. The strong smell is due to __

NH3 is the _________________________.

H2O is the _____________________

baseacid

Conjugate base

Conjugate acid

NH3

molecules


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What do you notice about water in the aboveexamples?

Amphoteric :A chemical species that behavesboth as an acid and as a base is called amphoteric.


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LiOH

NaOH

KOH

Ca(OH)2

Sr(OH)2

Ba(OH)

M-O.


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A specific strong acid - base reaction:

HCl(aq) + H2O(l)H3O+

(aq) + Cl-(aq)

HCl(aq) is the ___________________.

H2O(l) is the ________________.

H3O+

(aq) is the ________________________.

Cl-(aq) is the _________________________.

acid

baseConjugate acid

Conjugate base


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100% dissociation / good H+ donor

equilibrium lies far to right

HA H+ + A-

HCl H+ Cl- HCl H+ Cl-

Relative#moles

Beforedissociation

Afterdissociation


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. Relative Strengths of Acids and Bases (B/L)A) StrongAcid

No molecules of HA in water solution.

B)Weak Acid

An appreciable number of HB molecules exist in watersolution. Only a few H3O

+ ions and B- ions exist in the

solution.

An acid base reaction normally goes in the direction of


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An acid-base reaction normally goes in the direction ofthe weaker acid. You can use this fact to compare therelative strengths of any two acids.

If we have 0.10 M of the following acids, we obtain thefollowing results.

For acetic acid:

For hydrofluoric acid:

weaker


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CH3COOH and HF are __________ acids than H3O+.

HF is a __________ acid than CH3COOH.

weaker

stronger

In water all the strong acids are essentially 100%


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In water all the strong acids are essentially 100%ionized.

Is HCl stronger , weaker or equal to that of HI?

In water they are of equal strength since they both are100% ionized.

This is known as the leveling effect of water.


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.Strong acids form conjugate bases which have nomeasurable strength in water

Within a series of acids, the stronger the acid, theweaker the conjugate base, and the reverse is also true.

The _______ the acid the stronger the

________ base. What does this mean withrespect to these particles in solution?

weaker

conjugate


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Acids ConjugateBases

Increasestrength

Increasestrength

pH and the Self Ionization of Water


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pH and the Self Ionization of Water

In any sample of water, there are some ions which resultfrom the dissociation of water itself.


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Neutral solution

Kw= 1x 10-14


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[H+] > [OH-] are acidic solutions.

[OH-] > [H+] are basic solutions.


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You must keep in mind that in watersolutions of acids and bases there are

always OH- and H3O+ ions due to the selfionization of water.

These ions from water do not add manyions to reasonable concentrations of acidand base solutions, but you must

remember that they are there.


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Kw at 25oC = [H3O+] [OH-] = (1.0 X 10-7)2 = 1.0 X 10-14

If [H3O+] is 1.0 x 10-10 M then what is the [OH-] ?

Kw = [H3O+] [OH-]

1.0 X 10-14 = (1.0 X 10-10)[OH-]

1.0 X 10-4 = [OH-]


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LogLogLog

LogLogLogLog

Log

===

====

=

0.1 Mol/L0.01 M0.001 M

0.0001 M0.00001 M0.000001 M

0.0000001 M

-1-2-3

-4-5-6-7

-8

-(-1) = 1-(-2) = 2-(-3) = 3

Take our your

calculator


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The power of the hydrogen

pH = - log [H+]

What is the pH of a 0.5 M soln?

pH = -log[0.5]

= -(-0.301) = 0.301

Find the pH of a 3.8 x 10-4soln

H = 3.4


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The pH of a sample of water is 6.5.Calculate the molarity of the hydrogenion.

pH = -log[H+]

-pH = log [H+]

Inverse log = inverse log

Inverse log (pH) = [H+]

Inverse log (-6.5) = [H+] = 3.16 x 10-7


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If the pH of Coke is 3.12, [H+

] = ???pH = - log [H+]

- pH = log [H+]

Take antilog (10x

) of bothsides and get

10-pH =[H+]

[H+] = 10-3.12 = 7.6 x 10-4 M

*** to find antilog on your calculator, look for Shift or 2nd function

and then the log button


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A solution has a pH of 8.5. What is the

Molarity of hydrogen ions in thesolution?

pH = - log [H+]

8.5 = - log [H+]

-8.5 = log [H+]

Antilog -8.5 = antilog (log [H+])

10-8.5 = [H+]

3.16 X 10-9 = [H+]

K [H O+] [OH ]


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-log (1 x 10-14) = -log [H3O+] + - log [OH-]

14 = 7 7pKW = pH + pOH

Kw = [H3O+] [OH-]

1x 10-14 = 1 x 10-7 1 x 10-7

1 x 10-14

=[H3O+

] [OH-

]14 = pH + POH

=


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H+ OH-

[H+] >[OH-]

Acidic

solution

Basic

solution

[H+] =[OH-] [H+] 7pH = 7


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H

+

H+H+

OH

-

OH-OH-

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

Acidic Neutral Basic


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What is the pH of the

0.0010 M NaOH solution?

[OH-] = 0.0010 (or 1.0 X 10-3 M)

pOH = - log 0.0010

pOH = 3

pH = 14 3 = 11

OR Kw = [H3O+] [OH-]

1 x 10-14 = [H3O+] [ 1.0 X 10-3 ]

1.0 x 10-11 M = [H3O+]

H = - lo 1.0 x 10-11 = 11.00


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The pH of rainwater collected in a certainregion of the northeastern United States on

a particular day was 4.82. What is the H+

ion concentration of the rainwater?

The OH- ion concentration of a bloodsample is 2.5 x 10-7 M.

What is the pH of the blood?

1.51 x 10-5

7.39


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Paper tests like litmus paper and pH

paper Put a stirring rod into the solution

and stir.

Take the stirring rod out, and place

a drop of the solution from the endof the stirring rod onto a piece ofthe paper

Read and record the color change.

Note what the color indicates. You should only use a small

portion of the paper. You can useone piece of paper for several tests.


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Tests the voltage of theelectrolyte

Converts the voltage topH

Very cheap, accurate

Must be calibrated witha buffer solution


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Indicators are dyes that can be

added that will change color inthe presence of an acid or base.

Some indicators only work in aspecific range of pH

Once the drops are added, thesample is ruined

Some dyes are natural, likeradish skin or red cabbage


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Copyright by Houghton

Mifflin Company. All rightsreserved. 57


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1. Add solution from theburet.

2. Reagent (base) reacts withcompound (acid) insolution in the flask.

3. Indicator shows whenexact stoichiometricreaction has occurred.(Acid = Base)

This is calledNEUTRALIZATION.


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http://users.skynet.be/eddy/titratie.swf

Setup for titrating an acid with a base
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Setup for titrating an acid with a base


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http://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/buffe

r12.swf
http://users.skynet.be/eddy/titratie.swfhttp://users.skynet.be/eddy/titratie.swfhttp://users.skynet.be/eddy/titratie.swfhttp://users.skynet.be/eddy/titratie.swfhttp://users.skynet.be/eddy/titratie.swfhttp://users.skynet.be/eddy/titratie.swf


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Solutions of a weakconjugate acid-basepair.

They areparticularlyresistant to pHchanges, even when

strong acid or baseis added.


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If a small amount of hydroxide is added to anequimolar solution of HF in NaF, for example, the

HF reacts with the OH

to make F

and water.


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If acid is added, the F

reacts to form HF and water.


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The extent of ionization of a weak electrolyteis decreased by adding to the solution a strong

electrolyte that has an ion in common with theweak electrolyte.

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Chapt. 16 Acids and Bases (1)

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