Acids and Bases
Acids: The term acid, in fact, comes from the Latin term
acere, which means sour. Acids taste sour, are corrosive
to metals, change litmus (a dye extracted from lichens)
red, and become less acidic when mixed with bases.
Bases: Bases (also known as alkalies) feel slippery,
change litmus blue, and become less basic when mixed
with acids.
Neutralization: (Acid) + (Base) = (Salt) + (Water)
HCl + NaOH = NaCl + H2O
Where in the….S
What part of the tongue can taste
a lemon or other sour things?
http://www.miamisci.org/ph/phplumber.html
Answer
The green areas are where
you would taste sour foods
such as a lemon.
Where in the….B
Where might you taste
something bitter like
baking soda?
Answer
The green area is where you
would taste bitter foods such
as baking soda.
This tells you how not to take those bitter pills.
Acid Rain
Acid rain is rain that has been made acidic by certain pollutants in the air.
Acid rain is a type of acid deposition, which can appear in many forms.
Wet deposition is rain, sleet, snow, or fog that has become more acidic
than normal.
Dry deposition is another form of acid deposition, and this is when
gases and dust particles become acidic.
Both wet and dry deposition can be carried by the wind, sometimes for very
long distances. Acid deposition in wet and dry forms falls on buildings,
cars, and trees and can make lakes acidic. Acid deposition in dry form can
be inhaled by people and can cause health problems in some people.
Lifted from EPA website
pH-Table – EPA
http://www.epa.gov/acidrain/site_students/phscale.html
pH-Table continued
http://www.miamisci.org/ph/phplumber.html
Lemon Juice
4
Baking Soda
8
Aspirin
5
Ammonia
10
Milk of Magnesia
8
Lava Soap
10
Borax
9
Water
7
Lemon Soap
6
Vinegar
4
Tonic Water
4
Liquid Plumber
12
[H+]
pH-Table
Acids
Neutral
Bases
1 x 100
1 x 10-1
1 x 10-2
1 x 10-3
1 x 10-4
1 x 10-5
1 x 10-6
1 x 10-7
1 x 10-8
1 x 10-9
1 x 10-10
1 x 10-11
1 x 10-12
1 x 10-13
1 x 10-14
pH
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
Example
HCl - Hydrochloric acid
Stomach acid
Lemon juice
Vinegar
Soda
Rainwater
Milk
Pure water
Egg whites
Baking Soda
Tums® antacid
Ammonia
Mineral Lime - Ca(OH)2
Drano®
NaOH
Indicators
Indicators-- An indicator is a special type of compound
that changes color as the pH of a solution changes, thus
Gives us an approximate pH of the solution.
Many dyes (chemicals) are sensitive to hydrogen-ion
concentration. Beyond a certain threshold, they change
visible color and are used as indicators of the relative pH
of a solution.
Litmus paper - Paper with powder extracted from certain
plants that tests the pH of a substance. Acid turns red while
base turns blue; neutral remains white.
Phenolphthalein
 Phenolphthalein is a sensitive pH indicator
with the formula C20H14O4. Often used in
titrations, it turns from colorless in acidic
solutions to pink in basic solutions, the
color change occurring between pH 8 and
pH 10. If the concentration of indicator is
particularly strong, it can appear purple.
 http://en.wikimedia.org/wiki/Phenophthalein
 Phenolphthalein is insoluble in water, and
is usually dissolved in alcohol for use in
experiments.
 It is a colorless, weak acid, which can lose
H+ ions in solution. However, the
phenolphthalein ion is pink. When a base is
added to the phenolphthalein, the [atom 
ion] equilibrium shifts to the ionization
because H+ ions are removed.
Other indicators
 Other indicators:
 Indicator






pH of change
Methyl orange 4
Methyl red
5
Litmus
7
Bromthymol blue 7
Phenophthalein 9
Alizarin yellow 11
Color @ lower pH Color @ higher pH
Red
Red
Red
Yellow
Colorless
Yellow
Yellow
Yellow
Blue
Blue
Pink
Red
Make your own "litmus paper"
1. Chop the red cabbage up with a sharp knife.
2. Crush it with a "pestle and mortar" OR put it
in a food mixer and grind it.
3. Add a very small amount of water.
4. Decant the blue liquid (pour the liquid into a
clean glass).
5. Soak some blotting paper in the blue liquid.
6. Let the blotting paper dry out.
7. Cut the blue papers into small squares.
When you buy the red cabbage it is actually blue. It will be quite blue
when you slice it up and add some tap water. That is because your
tap water is very slightly alkaline. If you add some vinegar it will turn
red. This is because there is a pigment (coloured chemical) in the red
cabbage which acts as a pH indicator.
http://www.sambal.co.uk/indicators.html
Why is acid an acid?
All substances are made up of millions of tiny atoms.
These atoms form small groups called molecules. In
water, for example, each molecule is made up of two
hydrogen atoms and one oxygen atom. The formula
for a molecule of water is H2O. "H" means hydrogen,
"2" means 2 hydrogen atoms, and the "O" means
oxygen.
Why continued
When an acid is poured into water, it gives up H
(hydrogen) to the water. When a base is poured
into water, it gives up OH (hydroxide) to the water.
Stronger acids give up more protons (the positively
charged parts of atoms); stronger bases give up more
OH- (hydroxide). Neutral substances have an even
balance of protons and OH-.
Quantitative description of pH
pH = - log10 [H+]
[H+] = hydrogen ion concentration in units of
moles of H+ per liter of solution.
For example,
a solution with [H+] = 1 x 10-7 moles/liter has a pH 7
a solution with [H+] = 1 x 10-6 moles/liter has a pH 6
A simpler way to think about pH is that it equals the exponent
on the H+ concentration, ignoring the minus sign).
Human sense organs work logarithmically!!
Further Study
EPA: http://www.epa.gov/acidrain/site_students/whatisacid.html
http://www.shodor.org/unchem/basic/ab/#water
http://lrs.ed.uiuc.edu/students/erlinger/water/background/ph.html