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� What characterizes a molecule as an acid?
� What do all acids have in common?
Compound Formula Found in Electricalconductivity Taste
Citric acid HC6H7O7 Lemon juice Fair Sour
Phosphoric acid H3PO4 Gatorade Fair Sour
Acetic acid HC2H3O2 Vinegar Fair Sour
Boric acid H3BO3 Eyewash Fair SourOxalic acid H2C2O2 Rhubarb Fair Sour
Carbonic acid H2CO3 Soda pop Fair Sour
Hydrochloric acid HCl Stomach acid Good Sour in
dilute
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� All carry the name acid
� All conduct electricity to some degree
� All have sour taste� The element common to all members of the
group is hydrogen
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a. Produce H+ (as H3O+) ions in water (the hydronium
ion is a hydrogen ion attached to a water molecule)
b. Taste sour
c. Corrode metals
d. Electrolytes
e. React with bases to form a salt and water
f. pH is less than 7
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� What characterizes a molecule as a base?
� What do all bases have in common?
NaOH Sodium hydroxide Iye
KOH Potassium hydroxide Liquid soap
Ba(OH)2
Barium hydrox
ide Stabilizer forplastics
Mg(OH)2 Magnesium hydroxide Milk of magnesia
Al(OH)3 Aluminium hydroxide Antacid
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a. Produce OH- ions in water
b. Taste bitter, chalky
c. Are electrolytes
d. Feel soapy, slippery
e. React with acids to form
salts and water
f. pH greater than 7
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� Electrical conductivity:
Molecules came apart into ions
� Acids:
Molecule that ionized to give up hydrogen ions
A A-H H+
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Acids
produce H+ ions (or hydronium ions H3O+)
Bases
produce OH- ions
(problem: some bases dont have hydroxide ions)
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Acids proton donor
Bases proton acceptor
A proton is really just a hydrogen atom that has lost itselectron!
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� Acid is a proton donor� Base is a proton acceptor
Base Acid
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� Which of the following compounds could not
possibly an acid?
H2O CuSO4 NaHCO3 CH3COOH
� Why is your selection in question 1 correct?
� In the following reactions, which compound isthe acid?
HNO3 + NH4OH NH4NO3 + H2O
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HNO3 + H2O H3O+ + NO3-
Acid Base hydronium nitrate
ion ion
HNO3 + H2O H3O+ + NO3-
Acid Base
HNO3 + H2O Q H3O+ + NO3-
Acid Base conj. Acid conj. Base
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A Brønsted-Lowry acid is a proton donor
A Brønsted-Lowry base is a proton acceptor
acid conjugatebase
base conjugateacid
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Label the acid, base, conjugate acid, and
conjugate base in each reaction:
HCl + OH- Cl- + H3O +HCl + OH- Cl- + H3O +
H2O + HC2H3O2 C2H3O2- + H3O+H
2O + HC2H3O2 C2H3O2- + H3O+
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Increasingtendency to
capture Hydrogen
ion
Molecule or Ion Molecule or
Ion
Increasing
tendency to
give up
Hydrogen ion
Hydrobonate
ionxide ion
OH- + H+ H2O Water
Carbonate ion CO32- + H+
HCO3- Bicarbonate
ion
Ammonia NH3 + H + NH4+ Ammonium
ion
Bicarbonate ion HCO3- + H+
H2CO3 Carbonic
acid
Acetate ion C2H3O2- + H+
HC2O3O2
Acetic acid
Hydrogen
phosphate ion
H2PO4 + H+
H3PO4
Phosphoric
aicd
Sulfate ion SO42- + H+
HSO4- Bisulfate ion
Water H2O+ + H+ H3O+ Hydronium
ion
Nitrate ion NO3- + H+
HNO3 Nitric acid
Chloride ion Cl- + H + HCl Hydrochloric
acid
Bisulfate ion HSO4- + H+
H2SO4 Sulfuric acid
Perchlorate ion ClO4- + H +
HClO4 Perchloric
acid
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� Suppose that HCl is placed in water. Will HCl
give up a hydrogen ion to water, forming
hydronium ion and chloride ion?
� If acetic acid is placed in water, will the acetic
acid molecule donate a hydrogen ion to waterto make the hydronium ion?
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� Strong acid:
Transfer all proton to water,
Strong electrolyte
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Weak acids:
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Hydronium ion is found in a wide range of concentrations in water solutions.
Its concentrations ranges from 10-1 mol /
L (0.1 M
) in strongly acidic solutions to 10-14
(o.00000000000001 M) in strongly basic solutions
The term pH was developed to make it easier towrite about hydronium ion concentration
pH = - log [ H3O+]
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� pH = - log [H+] Remember the concentration [] means Molarity
Example: the concentration of hydronium ions inwater is :
[H3O+] = 0.0000001 mol/L
[H
3O+
] = 1x
10
-7
MAnd if pH =- log [H3O+]pH = - log [1o-7]pH = 7
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Example: If [H+] = 1 X 10-10
pH = - log 1 X 10-10
pH = - (- 10)pH = 10
Example: If [H+] = 1.8 X 10-5
pH = - log 1.8 X 10-5
pH = - ( - 4.74)
pH = 4.74
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Find the pH of these:
1) A 0.15 M solution of Hydrochloric acid
1) A 3.00 X 10-7 M solution of Nitric acid
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If the pH of Coke is 3.12, [H+] = ???
Because pH = - log [H+] then
- pH = log [H+]
Take antilog (10x) of bothsides and get
10-pH = [H+][H+] = 10-3.12 = 7.6 x 10-4 M
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� A solution has a pH of 8.5. What is the
Molarity of hydrogen ions in the solution?
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H2O can function as both an ACID and a
BASE.
In pure water there can beIn pure water there can beAUTOIONIZATIONAUTOIONIZATION
Equilibrium constant for water = Kw
Kw = [H3O+
] [OH-
] = 1.00 x 10-14
at 25 o
Cc
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Kw = [H3O+] [OH-] = 1.00 x 10-14 at 25 oCIn a neutral solution [H3O+] = [OH-]
so Kw = [H3O+]2 = [OH-]2
and so [H3O+] = [OH-] = 1.00 x 10-7 M
OH-
H3O+
OH-
H3O+
Autoionization
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� Since acids and bases are opposites, pH andpOH are opposites!
�
pOH does not really exist, but it is useful forchanging bases to pH.
� pOH looks at the perspective of a basepOH = - log [OH-]
Since pH and pOH are on opposite ends,pH + pOH = 14
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What is the pH of the
0.0010 M NaOH solution?
The OH- ion concentration of a blood sample is
2.5 x 10-7 M. What is the pH of the blood?