Transcript Introduction to Acids, Bases and pH

INTRODUCTION TO ACIDS, BASES
AND PH
Lesson 13
PROPERTIES OF ACIDS AND BASES
Acids
 Acids are traditionally considered any chemical
compound that, when dissolved in water, gives
a solution with a hydrogen ion activity greater
than in pure water, i.e. a pH less than 7.0. They
also:
 Taste sour
 Are good conductors of electricity (they
release H+ ions when they are in water)
 React with compounds that contain
carbonate
 Are generally quite reactive
 Turns litmus red
When Acids are dissolved in water they release
H+ .
 Ex
 HCl(aq)  H+(aq) + Cl-(aq)



Acids are widely used in industry, they are used
in many manufacturing processes including;
fertilizers, explosives, refining oil, and
electroplating materials.
Table 1 Examples of common acids include
Common name
Formula
Source or use

Vinegar (acetic
acid)
Citric acid
HC2H3O2
Salad dressing
HC6H7O7
Oranges, lemons
Ascorbic acid
HC6H7O6
Vitamin C
Lactic acid
HC3H5O3
Sulfuric acid
H2SO4
Sour milk or tired
muscles
Car batteries
BASE
A base is most commonly thought of as an
aqueous substance that can accept hydrogen
ions.
 bases can commonly be thought of as any
chemical compound that, when dissolved in
water, gives a solution with a hydrogen
ion activity lower than that of pure water, i.e.
a pH higher than 7.0 at standard conditions.
They also:

Taste bitter
 Are good conductors of electricity (They
release OH- ions when dissolved in water)
 Break down proteins into smaller molecules
 May also be called alkaline
 Turns litmus blue

When bases are released in water they release
OH- ions
 Example
 NaOH (aq)  Na+ (aq) + OH- (aq)

TABLE 2 EXAMPLES OF SOME COMMON
BASES
Common Name
Formula
Source or use
Sodium
hydroxide
NaOH
Drain cleaner
Potassium
hydroxide
KOH
Soap, cosmetics
Aluminum
hydroxide
Al(OH)3
Antacids
Ammonium
hydroxide
NH4OH
Window cleaner.
FORMULAS FOR ACIDS AND BASES
Acids
 Common acids can be recognised because their
formula begins with (H) hydrogen.
 Examples:
H2SO4
H2CO3
H3PO4
HCl
Bases
 Bases are not as easy to recognise, most will
contain a hydroxyl group (OH-).
 Ex: NaOH, Mg(OH)2

Other compounds can form bases when they react
with water to form OH- ions. Compounds that
contain carbonate (CO32-) or bicarbonate (HCO3-)
react
THE PH SCALE
The pH scale is used to represent how acid or
basic a solution is. The scale ranges from 0-14
with very acidic being 0, neutral being 7, and
very basic being 14.
 Every point on the scale represents a 10 base
exponent difference.
 Ex lemons (pH = 2.0) are 100 times more
acidic than tomatoes (pH = 4.0)
 7.0 is neutral (neither acidic nor basic (alkaline)).
 Acids range from 0-6.9
 Bases range from 7.1 -14

THE PH SCALE