2. HCl(g)  H+(aq) + Cl-(aq)
Acids
A Swedish chemist, named Arrhenius in 1890 proposed that an acid be
defined as any substance that, when added to water, increases the hydronium
ion concentration. Hydronium is defined as H3O+.
Water will attract a H+ ion to produce a hydronium ion.
H2O + H+  H3O+
Many times we will only write the H+ to represent the hydronium ion.
For example if HCl(s) is added to water the following will occur.
HCl(g)  H+(aq) + Cl-(aq)
H2O(l) + H+(aq)  H3O+(aq)
Adding the two reactions together
HCl(g) + H2O(l)  H3O+( aq) + Cl-(aq)

3. HOCl(l) + H2O(l)  H3O+(aq) + ClO−(aq)
Strong Acids vs. Weak Acids
Strong acids will tend to go to completion when dissolved in water, weak
acids do not.
HOCl(l) + H2O(l)  H3O+(aq) + ClO−(aq)
Weak Acid
HNO3(l) + H2O(l)  H3O+(aq) + NO3−(aq)
Strong Acid

4. KOH(s)  K+(aq) + OH-(aq)
Bases
Arrhenius defined bases as any substance when dissolved in water will
produce hydroxide ions. (OH-)
KOH(s)  K+(aq) + OH-(aq)
If they go to completion when dissolved in water they are said to be strong
bases, if they do not dissolve well and produce few hydroxide ions they are
called weak bases.
Another term used to describe basic solutions is alkaline. An alkaline solution
is very basic. This term comes from group 1 of the periodic table which always
makes strong basic solution.

5. The definitions of Arrhenius acid and Arrhenius base given earlier in this
book are variants of the definitions of acid and base originally proposed
by Arrhenius in the late 19th century. One drawback that the Arrhenius
definitions have is that they are limited to aqueous solutions: HCl, for
instance, should be considered an acid whether it is in the form of a pure
gas or in aqueous solution. Another limitation is that the Arrhenius definition
cannot classify substances that sometimes act as acids and sometimes
act as bases.
Brønsted-Lowry Acids
In 1923, the Danish chemist Johannes Brønsted proposed a broader definition
of acid. Surprisingly, the same year, the British scientist Thomas Lowry
happened to make exactly the same proposal independently. Their
idea was to apply the name acid to any species that can donate a proton.
Recall that a proton is a hydrogen atom that has lost its electron; it is a
hydrogen ion and can be represented as H+. Such molecules or ions are
now called Brønsted-Lowry Acids. Proton acceptors are called
Brønsted-Lowry Bases.

7. H2S + H2O → H3O+ + HS− Lost a proton, H+, therefore
is the acid.
Gained a proton, H+, therefore
is the base.

8. Properties of Acids and Bases
Are excellent electrolytes
Are excellent electrolytes
Have a pH below 7
Have a pH above 7
Will react with many metals
to produce hydrogen gas
Are said to be basic or
alkaline
Are said to be acidic

9. Acids will react with metal to produce hydrogen gas
The proton, H+, will react with many metals to produce
hydrogen gas using a single displacement reaction.
Any metal located above the H2 on table J will react
with an acid to produce hydrogen gas.

10. Mg + HCl  Na + HCl  Cu + HCl  Zn + HCl 
Write out the chemical react that will occur between the listed acid and metal
Mg + HCl 
Na + HCl 
Cu + HCl 
Zn + HCl 

11. H+(aq) + Cl-(aq) + K+(aq) + OH-(aq) 
Neutralization
Neutralization reaction the reaction of the ions that characterize acids
(hydronium ions) and the ions that characterize bases (hydroxide ions) to
form water molecules and a salt (ionic compound).
HCl(aq) + KOH(aq) 
Acid Base
H+(aq) + Cl-(aq) + K+(aq) + OH-(aq) 
H2O(l) + KCl(aq)
Water Salt

12. pH
A value used to express the acidity or alkalinity of a solution; a pH of 7
is neutral, a pH of less than 7 is acidic, and a pH of greater than 7 is basic
pH < 7
pH = 7
pH > 7
Water is neutral because it is made up of one acid (H+), and one base (OH-).

13. pH factors of 10
Each pH number indicated a change of concentration of hydronium ion
concentration by a factor of 10.
For example:
If a sample of pool water has a pH of 8 and after adding chlorine for cleaning
the pH changes to 5 how much has the hydronium ion concentration changed? pH
8    5
x x
10 x 10 x10 = 1000
The hydronium ion concentration changes by a factor of 1000
Because pH is dropping into the acid range, this indicated an increase in
hydronium ion concentration.

14. Indicators
Certain dyes, known as indicators turn different colors in solutions of
different pH.
Dozens of indicator dyes are available. Some indicators, such as litmus,
are natural products, but most are synthetic. Each indicator has its
own colors and its individual range of pH over which it changes shade. By
suitably blending several indicators, chemists have prepared “universal
indicators,” which turn different colors throughout the entire pH range.

15. Titrations
The gradual addition of one solution to another to reach an equivalence point is called a titration. The purpose of a titration is to determine the concentration of an acid or a base. In addition to the two solutions, the equipment needed to carry out a titration usually includes two burets, a titration flask, and a suitable indicator.
The formula used for titrations is from your
reference tables.

16. A solution of a base differs from a solution of an acid in that the solution of a base
1. is able to conduct electricity
2. is able to cause an indicator color change
3. has a greater [H3O+]
4. has a greater [OH-]
Which pH value indicates the most basic solution?
1. 7
2. 8
3. 3
4. 11
A 3.0-milliliter sample of HNO3 solution is exactly neutralized by 6.0 milliliters
of 0.50 M KOH. What is the molarity of the HNO3 sample? M M M M

17. Which solution will turn litmus from red to blue?
1. H2S(aq)
2. NH3(aq)
3. SO2(aq)
4. CO2(aq)
Which substance is always produced in the reaction between hydrochloric acid
and sodium hydroxide?
1. water
2. hydrogen gas
3. oxygen gas
4. a precipitate
Equal volumes of 0.1 M NaOH and 0.1 M HCl are thoroughly mixed.
The resulting solution has a pH closest to
 1. 5
 2. 7
 3. 3
 4. 9

18. As an aqueous solution becomes more acidic, the hydroxide ion concentration
1. decreases
2. increases
3. remains the same
What produces hydrogen ions as the only positive ions in aqueous solution?
1. KOH
2. HBr
3. NH3
4. NaCl
When the pH of a solution changes from a pH of 5 to a pH of 3, the hydronium
ion concentration is
of the original content
of the original content
3. 10 times the original content
times the original content