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41 Cards in this Set

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Arrenheius Acid and Base
Acid: anything that produces hydrogen ions in aqueous solution

Base: anything that produces hydroxide ions in aqueous solution

** only for aqueous solutions
Brondsted and Lowry Acids and Bases
acid: anything that donates a proton
base: anything that accepts a proton
Lewis Acids and Bases
Acid: anything that accepts a pair of electrons

Base: anything that donates a pair of electrons

-includes all Bronsted and Lowry definitions and more
-include molecules that have an incomplete octet of electrons around the centrol atom ex. AlCl3, BF3
-include simple cations except alkali and heavier alkaline earth metal cations

Fe3+ common Lewis Acid
hydrogen ion concentration measurement
pH=-log[H+]

ex. H+ concentration = 10^-3
pH=-log[10^-3]
pH=3

logAB = logA +logB
Acid with pH of 2 produces 10 times as many hydrogen ions as an acid with a pH of 38
HA+H20--> A- +H30+
HA= acid (donates hydrogen)
A-= conjugate base

H20=base (accepts proton)
H30+= conjugate acid

The stronger the acid the weaker the conjugate base, the stronger the base the weaker the conjugate acid.

Look out!
Weak acids can have strong or weak conjugate bases.

H20
Amphoteric
-substances that can act either as an acid or base: H20
Acid and Base characteristics
-Acid: sour or tart
-Base: bitter, slippery when wet

Kw=KaxKb
Strong acids
HI hydroiodic acid
HBr hydrobromic acid
HCl hydrochloric acid
HNO3 nitric acid
HClO4 perchloric acid
HClO3 chloric acid
H2SO4 sulfuric acid
Arrenheius Acid and Base
Acid: anything that produces hydrogen ions in aqueous solution

Base: anything that produces hydroxide ions in aqueous solution

** only for aqueous solutions
Brondsted and Lowry Acids and Bases
acid: anything that donates a proton
base: anything that accepts a proton
Lewis Acids and Bases
Acid: anything that accepts a pair of electrons

Base: anything that donates a pair of electrons

-includes all Bronsted and Lowry definitions and more
-include molecules that have an incomplete octet of electrons around the centrol atom ex. AlCl3, BF3
-include simple cations except alkali and heavier alkaline earth metal cations

Fe3+ common Lewis Acid
hydrogen ion concentration measurement
pH=-log[H+]

ex. H+ concentration = 10^-3
pH=-log[10^-3]
pH=3

logAB = logA +logB
Acid with pH of 2 produces 10 times as many hydrogen ions as an acid with a pH of 38
HA+H20--> A- +H30+
HA= acid (donates hydrogen)
A-= conjugate base

H20=base (accepts proton)
H30+= conjugate acid

The stronger the acid the weaker the conjugate base, the stronger the base the weaker the conjugate acid.

Look out!
Weak acids can have strong or weak conjugate bases.

H20
Amphoteric
-substances that can act either as an acid or base: H20
Acid and Base characteristics
-Acid: sour or tart
-Base: bitter, slippery when wet

Kw=KaxKb
Strong acids
HI hydroiodic acid
HBr hydrobromic acid
HCl hydrochloric acid
HNO3 nitric acid
HClO4 perchloric acid
HClO3 chloric acid
H2SO4 sulfuric acid
Strong Bases
NaOH - sodium hydroxide
KOH - potassium hydroxide
NH2 - amide ion
H - hydride ion
Ca(OH)2 - calcium hydroxide
Na2O - Sodium Oxide
CaO- Calcium Oxide

-completely dissociate
Acid dissociation and concentration
Acid dissociation decreases with acid concentration

Acid strength increases with acid concentration
Oxyacids
more oxygens means a stronger acid,
-more oxidations more polar, can stablaize bond from conjugate base
acidity increases as does oxidation of central atom
Whether an H is donated from molecular structures
3 factors
-strength of bond holding hydrogen to molecule
-polarity of bond
-stability of conjugate base

ex. CH3 vs. HCl
same bond strength
-CH3 not polar
HCl polar: proton easily removed in aqueous solution

Hydrogen Halides:
H-F HCl H-Br H-I

bond strength and polarity increases right to left
-bond strength and weakness of conjugate base outweigh polarity and acidity increases left to right
Hydrides
-compound with only two elements one being Hydrogen

-increases from left to right and top to bottom on a periodic table
Lecture question 124
Which of the following is amphoteric:

1) amino acid
2)H2SO4
3)NaOH
4)HF
Amino Acids are amphoteric
Which of the following is the strongest base:

1) Cl-
2) NH4+
3) F-
4) Br-
Look for weak conjugate acid

HF
Equillibrium Constants for Acid-Base reactions
autoionization of water
Kw=[H+][OH-]=10^-14
For an aqueous solution at 25
pH+ pOH= pKw =14
acid dissociation constant Ka
HA+ H20 --> H30+ + A-

Ka = [H+][OH-]/[HA]
bsae dissociation constant Kb
complements the Ka

kb= [OH-][HA]/[A-]

KaKb= kw
LQ 129: What is Kb for conjugate base of carbonic acid?
-react carbonic acid HCO3- with water and get H2C03 + OH-

Kb= [OH-][H2CO3]/[HCO3-]
LQ 131: Ka of 4.3 x 10^-7

What is pH of 1 mole of NaHCO3 in 1 liter of water
HCO3- will act as a base
Find Kb from Kw/Ka
set it equal to (x)(x)/(1-x)

because thats how many ions of OH- and conjugate acid will dissociate

x in (1-x) is negligible so get rid of it.

kb= x^2 find x...that is pOH
find pH from that

answer:10
Titration
-drop by drop mixing of an acid and a base in order to find concentration of unknown
equivalence point of titration
point in titration where equal equivalents of acid and base are in solution

-for strong acid base titrations teh equivalence point will be at pH7
-titration of weak acid with strong base has equivalence point above 7 and strong acid with weak base below 7
half equivalence point
-point where one half of the acid has been neutralized by base
-concentration of acid = concentration of conjugate bsae
-occurs at midpoint section of graph that most resembles a horizontal line
-point is where solution is most well buffered
-pH=pKa
Henderson-Hasselbach equation
pH= pKa +log[A-]/[HA]
another expression for ka
-does not allow for ion pairing
buffer solution
-start with acid whose pKa is closest to the pH which we want to buffer
-add equal amounts of acid with its conjugate base and lots of it
-solution wont change pH as quickly
Indicators and the End point
-to find equivalence point use an indicator, a weak acid whose conjugate base is a different color
-range = pKa-1 to pKa +1
-where it changes color is the endpoint, not equivalence point
Polyprotic titrations
-have two half equivalence points and 2 equivalence points
-each for when 1 H is lost
LQ 138

What acid should be used to manufacture a buffer at a pH of 6.1
to make a buffer at a certain pH use an acid which has the closest pKa
LQ 139
What would be the best indicator for a titration with an equivalence point at pH of 8.2
-find pKa of indicators, and calculate its range by adding 1 and subtracting one, and if the range covers the equivalence point then that indicator should be used.
LQ 142
How to make a buffer solution?
Mix equal concentrations of an acid with a pKa close the the pH where we want our solutoin with its conjugate base.
Q 138
If ratio of acetic acid to its conjugate base is 10 to 1, what is approximate pH of the solution?
Ka= 1.8E10^-5
ph= pka + log (base/acid)
4.7 + log(.1)
4.7 -1 =3.7

log anything less than one is negative number
Q131

Is H2SO4 a stronger acid than
1) H2O
2) H3O+
3) H2SO3
Lowest Pka is strongest acid. Sulfuric acid is strongest acid!
q 124
As temperature increases,
what happens to the pH of pure water
hydrogen ions increase, pH decreases