Chemistry 3.3

Chemistry
Chapter 3 - Section 3

Acidic and
Basic Solutions


Wednesday, July 11, 2012

Why So Sour?


Why So Sour?

The acid causes the sour taste of
these and other foods.

Acids ?


Substances that RELEASE positively
charged hydrogen ions, H+, in water.


When an acid mixes with
water, the acid dissolves,
releasing a hydrogen ion.


The hydrogen ion then
combines with a water
molecule to form a
hydronium ion, H30 +.


Hydronium Ion ?


positively charged ion with
the formula H3O +


Properties of Acids
๏Tastes Sour
๏Conducts Electricity
๏The hydronium ions in an acidic solution can
carry the electric charges in a current

๏Corrosive
๏They can break down certain substances. Many
acids can corrode fabric, skin, and paper.


Properties of Acids
๏React with metals
๏The solutions of some acids also react
strongly with certain metals.
๏The acid-metal reaction forms metallic
compounds and hydrogen gas, leaving holes
in the metal in the process.


Uses of Acids


Uses of Acids

Acetic Acid


Uses of Acids

Citric Acid


Uses of Acids

Ascorbic
Acid


Uses of Acids

Sulfuric Acid

Uses of Acids

Acids often are used in batteries because their
solutions conduct electricity

Uses of Acids
Hydrochloric acid, which is
known commercially as muriatic
acid, is used in a process called
pickling. Pickling is a process
that removes impurities from
the surfaces of metals.


Acidsin the

Environment


Acidsin the

Environment
Carbonic
acid
plays a key role in
the formation of
caves and of
stalactites and
stalagmites.


Acidsin the

Environment

Carbonic acid is
formed when
carbon dioxide in
soil is dissolved in
water.


Acidsin the

Environment
When this acidic
solution comes
in contact with
calcium
carbonate—or
limestone rock
—it can dissolve
it, eventually
carving out a
cave in the rock.

Now on to...


Bas
es


Bases?


substances that can
ACCEPT hydrogen ions.


Do you remember the
definition of an acid?


Substances that
RELEASE positively
charged hydrogen
ions, H+, in water.


Substances that release positively
charged hydrogen ions, H+, in water.

Acids

Bases
Substances that can accept hydrogen
ions.

When a base dissolves in water,
some hydrogen atoms from the
water molecules are attracted to
the base.


A hydrogen atom in the water
molecule leaves behind the
other hydrogen atom and
oxygen atom.


Base + H2O 


Base + H2O 
H
Base + HO 


Base + H2O 
H
Base + HO 
H
Base + HO- 


What is left of the H2O is the OH-, which
an ion called a hydroxide ion.


Most bases contain a
hydroxide ion, which is
released when the base
dissolves in water.


For example, sodium
hydroxide is a base with the
formula NaOH.
When NaOH dissolves in
water, a sodium ion
and the hydroxide ion


Properties of Bases

๏Basic solutions feel slippery.
๏Bases also taste bitter.
๏Like acids, bases are corrosive.
Basic solutions contain ions and can
conduct electricity.
๏Basic solutions are not as reactive with
metals as acidic solutions are.


Where do we find
Bases?


Where do we find
Bases?

soaps,
ammonia,
cleaning
products

Where do we find
Bases?
The hydroxide
ions produced
by bases can
interact strongly
with certain
substances, such
as dirt and
grease.


Where do we find
Bases?

chalk

Where do we find
Bases?

blood

pH??


a measure of how
acidic or basic a
solution is


pH

๏The pH scale ranges from 0 to 14.
๏Acidic solutions have pH values below 7.
๏A solution with a pH of 0 is very acidic.
๏A solution with a pH of 7 is neutral.
๏Basic solutions have pH values above 7.


pH


A change of 1 pH unit represents a tenfold
change in the acidity of the solution.


For example, if one solution has a pH of 1 and
a second solution has a pH of 2, the ﬁrst
solution is not twice as acidic as the second
—it is ten times more acidic.


To determine the difference in pH strength,
use the following calculation:
10 n,

where
n = the difference between pHs.

For example: pH3 - pH1 = 2

10 2 = 100 times more acidic.


Strength of
Acids and Bases
๏The difference between food acids and the
acids that can burn you is that they have
different strengths.


Strength of Acids and Bases


Hydrochloric acid separates into ions
more readily than acetic acid does
when it dissolves in water.
The more easily a H+ ion is released,
the stronger the acid is.


Therefore, hydrochloric acid exists in water
as separated ions. Acetic acid exists in
water almost entirely as molecules.


More hydronium ions means a stronger-
acid solution. It would have a lower pH
than the weak-acid solution.


The strength of a base is related to
how easily the base accepts H +, or

how easily a hydroxide ion is made,
when the base dissolves in water.


Neutra
lizatio
n


Neutralization??


the reaction of an acid with a base. It is called this
because the properties of both the acid and base
are diminished, or neutralized.


In most cases, the
neutralization reaction
produces a water and a
salt.


How does
neutralization occur??

๏Recall that every water molecule
contains two hydrogen atoms and one
oxygen atom.
๏When one hydronium ion reacts with
one hydroxide ion, the product is two
water molecules. This reaction occurs
during acid-base neutralization.


How does


How does

๏Equal numbers of hydronium ions from
the acidic solution and hydroxide ions
from the basic solution react to produce
water.
๏Pure water has a pH of 7, which means
that it’s neutral.


Indica
tors


Indicators??


are compounds that react
with acidic and basic solutions
and produce certain colours,
depending on the solution’s
pH.


Because they are different
colors at different pHs,
indicators can help you
determine the pH of a
solution.


When litmus paper is placed
in an acidic solution, it turns
red. When placed in a basic
solution, litmus paper turns
blue.


Finish
ed!


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