Acids and Bases
Chemistry
Module
B
7
Textbook Chapter 20 & 21
Acids
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Give up H+ when dissolved in water
Turn litmus red
Clear in Phenolphthalein
Sour taste
Has pH < 7
Reacts with metal to form hydrogen
(H2) gas
Naming Acids (Review)
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Acids start with Hydrogen
Binary acids are Hydro___ic Acid
Ternary acids take their name from the
polyatomic ion
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Sulfate ion is Sulfuric Acid (H2SO4)
Nitrite ion is Nitrous Acid (HNO2)
Bases
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Gives up (OH)- when dissolved in
water
Turns litmus blue
Pink in Phenolphthalein
Bitter taste
Feels slippery
Has pH > 7
Naming Bases (Review)
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Page 2 of
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Write the name of the metal and roman
numeral (if needed)
Add the hydroxide
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NaOH is Sodium hydroxide
Fe(OH)2 is Iron (II) Hydroxide
Acid-Base Theories
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Arrhenius Acidsubstance that
produces a
hydrogen ion in
solution
Bronsted Lowry
Acid- hydrogen ion
donor
Lewis Acids Accepts a pair of
electrons.
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Arrhenius Base –
a substance when
in a water solution
gives up an (OH)-1
Bronsted Lowry
Base – hydrogen
ion acceptor
Lewis Bases- An
electron pair donor
Strong vs. Weak Bases
Page 4 of
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A base is strong if it contains a group I or
II metal; ionizes completely
 Ex. NaOH
 A base is weak if it contains any other
metal or (NH4)+; ionizes slightly
Strong or Weak Acids?
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There are only 6 strong acids: You must learn them.
The remainder of the acids therefore are
considered weak acids.
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Page 4 of
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HCl
H2SO4
HNO3
HClO4
HBr
HI
Note: when a strong acid dissociates only one H+ ion is
removed. H2S04 dissociates giving H+ and HS04- ions.
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H2SO4 → H+ + HSO41A 0.01 M solution of sulfuric acid would contain 0.01 M H+ and
0.01 M HSO41- (bisulfate or hydrogen sulfate ion).
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Common Acids and their Uses
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Hydrochloric acid (HCl) in gastric juice
Sulphuric acid (H2SO4)
Nitric acid (HNO3)
Carbonic acid in softdrink (H2CO3)
Uric acid in urine
Ascorbic acid (Vitamin C) in fruit
Citric acid in oranges and lemons
Acetic acid in vinegar
Tannic acid (in tea and wine)
Tartaric acid (in grapes)
Common Bases/Uses
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Sodium hydroxide (NaOH) or caustic soda
used to make soap and biodiesel, plus
much more!
Calcium hydroxide ( Ca(OH)2 ) or limewater
Ammonium hydroxide (NH4OH) or ammonia
water - a household cleaner
Magnesium hydroxide ( Mg(OH)2 ) or milk of
magnesia – used as an antacid or a laxative
Many bleaches, soaps, toothpastes and
cleaning agents
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Conjugate Acids and Bases
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Based on the work by Bronsted-Lowery
Examples:
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HCl + NaOH =>
acid
base
proton proton
donor acceptor
HCl
acid
+
NH3
base
NaCl +
H 2O
conjugate conjugate
base
acid
=>
NH4+ +
conjugate
acid
Clconjugate
base
Sample Problems
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Label the reaction with the following: Acid, base,
conjugate acid, conjugate base
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F-1 + H2O  HF + OH-1
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NH3 + H-1  NH2-1 + H2
pH Scale
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relationship between [H+]
and pH
 pH = -log [H+]
Definition of acidic, basic,
and neutral solutions based
on pH
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acidic: if pH is less than 7
basic: if pH is greater than 7
neutral: if pH is equal to 7
Explore
Page 7 of
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Indicators
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Page 7 of flip book
Acid - Base indicators (also
known as pH indicators) are
substances which change color
with pH.
They are usually weak acids or
bases, which when dissolved
in water dissociate slightly and
form ions.
http://www.elmhurst.edu/~chm/vchembook/180acidsbases.html
Other pH indicators
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Cabbage Juice
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Red-acid
Blue-base
Strawberry Juice
Universal Indicator
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http://www.seed.slb.com/en/scictr/lab/food_ph/res.htm
pH 2 - pink
pH 4 - Orange
pH 6 - Yellow
pH 8 - Aqua/Blue
pH 10 - Blue
pH 12 - Violet
http://encarta.msn.com/media_1461500642/Universal_Indicator.html
pH Calculation
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Convert to Molarity and put into the pH equation
scientific calculators are a MUST for most of these.
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1) 0.0015
2) 5.0 x 10¯9
3) 1.0 x 10-3
4) 3.27 x 10¯4
5) 1.00 x 10¯12
6) 0.00010
pH = -log[H+]
pH + pOH = 14
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pOH is based on the concentration of
hydroxide ion.
pOH = -log[OH-1]
pH + pOH = 14
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Neutralization
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Neutralization
one type of double replacement
reaction
Acid + Base  Salt + water
Net ionic equation shows what drives
the neutralization reaction
HCl(aq) + NaOH(aq)  NaCl(aq) +
H2O(l)
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Neutralization Problems
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HBr + Ca(OH)2 ------->
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How many moles of Ca(OH)2 will it take to
neutralize 15 moles of HBr?
Steps
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1. Write a balanced neutralization reaction
2. Identify want and given
3. Convert given to moles M x L = Moles
4. Convert moles of given to moles of want by
using coefficients. (ratio)
5. Calculate the molarity of want = Moles/L = M
Sample Problem
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When 45.0 mL of 3.00 M HBr is added
to 80.0 mL of Ca(OH)2 What is the
molarity of the Ca(OH)2 that was
neutralized?
Titration Concepts
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Titration- The process
which involves finding the
concentration of an
unknown solution by using
a certain volume of a
known solution.
End point- The point
where neutralization is
achieved and the indicator
has changed color.
Page 11 of
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Titration Equation
MacidVacid = MbaseVbase
Hydrolysis of Salts
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definition of a salt:
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an ionic compound made of a cation and an
anion, other than hydroxide.
the product besides water of a neutralization
reaction
When you place a salt in water you get an
acid and a base.
Then you have to determine if your new
solution is acidic or basic
Determining acidity or basicity of a salt solution
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split the salt into cation and anion
add OH- to the cation
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a. if you obtain a strong base. the
cation is neutral
b. if you get a weak base, the cation
is acidic
Add H+ to the anion
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a. if you obtain a strong acid, the
anion is neutral
b. if you obtain a weak acid. the anion
is basic
Determining acidity or basicity
of a salt solution, cont.
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Salt solutions are neutral if both ions
are neutral
Salt solutions are acidic if one ion is
neutral and the other is acidic
Salt solutions are basic is one of the
ions is basic and the other is neutral.
The acidity or basicity of a salt made
of one acidic ion and one basic ion
cannot be determined without further
information.
Acidic, Basic or Neutral?
Strong Acid
Strong Base
Neutral Salt
Strong Acid
Weak Base
Acidic Salt
Weak Acid
Strong Base
Basic Salt
Weak Acid
Weak Base
Neutral Salt
Sample Problems
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1. Cu(NO3)2
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2. KC2H3O2
Sample Answer
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An aqueous solution of KC2H3O2 will
be basic. The K+ is the cation of a
strong base (KOH), thus it is a neutral
ion and has no effect on the pH of the
solution. The C2H3O2- is from a weak
acid (HC2H3O2), thus it is a basic ion.
This compound in an aqueous solution
will, therefore, form a basic solution.
Sample Problem Answer
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An aqueous solution of Cu(NO3)2 will
be acidic. The Cu2+ is the cation of a
weak base (Cu(OH)2), thus it is an
acidic ion and has an effect on the pH
of the solution. The NO3- is from a
strong acid (HNO3), thus it is a neutral
ion. This compound in an aqueous
solution will, therefore, form an acidic
solution.