ACID BASE CHEMISTRY
TECH 51 – SYRACUSE 14
REVIEW
The following slides are intended to serve as an
overview of your text, not a replacement. You are
responsible for all material in the chapter. Some of
the information has been simplified as the
course is an OVERVIEW and not intended to be
a high school chemistry class.
DEFINITIONS
If you read most science texts about acids and bases
you will read that acids always produce hydrogen ions
(H+) and bases produce hydroxide ions (OH-). But
this can get you into trouble as it does not account
for a lot of chemicals that have properties of acids
and bases where the ions mentioned may not be
present.
Acids
An acid is defined as any substance that gives away or
liberates a hydrogen ion. Remember that a hydrogen
ion is a proton.
FOR THIS REASON, AN ACID IS
REFERRED TO AS ANY SUBSTANCE THAT
IS A PROTON DONOR.
Hydrogen Ion
So an acid liberates a hydrogen ion. Since a hydrogen
ATOM is composed of ONE proton and ONE
electron, then the ion must be different. Hydrogen
DOES NOT want to lose the electron, but it is a very
small atom and it loses most “tug of wars” with larger
atoms. This results in a single proton with no electron.
The proton goes crazy and seeks out electrons. This is
where water comes into play.
Hydronium Ion
• A hydronium ion is formed when the proton from
the Hydrogen Ion combines with a molecule of
water. If you remember, water is covalently bonded
and the atoms share electrons unevenly. This means
that the proton, with a positive charge, will combine
to the negatively charged part of the water molecule.
-SEE NEXT SLIDE-
HYDRONIUM ION
WHEN THE WATER ACTS AS A
BASE AND ACCEPTS THE
PROTON THE ION THAT
FORMS IS CALLED A
HYDRONIUM ION.
NOTICE THAT IT IS ACTUALLY
A POLYATOMIC MOLECULE
WITH A CHARGE OF +1.
See the next slide for a different
example.
Here you see two different pictures showing the same thing. For a
hydronium ion to form, the hydrogen ion combines with the water to
form the hydronium ion. Technically, the acid is the H3O+ but we
will write it as H+.
HERE YOU CAN SEE THAT WHEN HCl IS ADDED TO WATER, THE WATER
ACTUALLY ACTS LIKE A BASE. HOW? SINCE THE HCl GIVES A PROTON, IT IS
AN ACID (BY DEFINITION see previous slide 4). SINCE THE WATER IS
ACCEPTING THE PROTON IT BECOMES A BASE (AGAIN, BY DEFINITION, see
slide 5).
BASES
Bases receive protons, so by this definition, a base is
defined as any substance that receives a hydrogen
ion.
BASES ARE PROTON ACCEPTORS.
(or proton receiver)
Years ago, bases were defined as anything that liberated (gave off)
a OH- ion, but this definition did not account for many things
that had properties of a base but no OH.
HYDROXIDE IONS
Hydroxide ions can be formed when substances are
added to water, such as ammonia, or liberated when
compounds dissociate in water releasing hydroxide
ions. For example, when the substance NaOH is
added to water, it separates forming Na+ and OH-.
Ammonia
When ammonia (NH3) is added to water it acts as a base as
it is a proton acceptor. This results in the formation of
a OH- ion.
NOTICE THAT THIS MEANS THAT WATER IS NOW AN ACID.
EARLIER IT WAS A BASE.
AMPHOTERIC
This is the term that is given to a substance that has
about the same ability to behave as an acid as it does
a base. Since water behaves in this way, it is a good
example of a substance that is amphoteric.
PROPERITES
ACIDS-proton donor
• Taste sour
• pH less than 7
• Turn litmus red
• Neutralize base
• + metal  H2
• Conduct electricity
• Turn congo red blue
BASES-proton acceptor
• Taste bitter
• pH greater than 7
• Turn litmus blue
• Neutralize acid
• Feel slippery
• Conduct electricity
• Turn PHTH pink
SALT
When you are sitting at the dinner table and your
parents ask you to “pass the salt” they are asking
specifically for NaCl. It is a salt though, because it is
a metal, Na+, and a nonmetal, Cl-.
By definition though,
A SALT IS ANY IONIC COMPOUND
FORMED WHEN A METAL AND ANY
NONMETAL COMBINE, except H and OH
(this forms water, covalently bonded)
STRENGTH
What makes a substance have the characteristics of an acid or base
is the ability to form ions. When an acid or base forms
ions then the characteristics of an acid or base form.
If ions form easily, then a substance is said to be
STRONG. If a chemical does not form ions easily,
then it is said to be WEAK. This goes against what you
might think as a strong bond will hold onto an atom
more tightly than a weaker bond.
CONCENTRATION
It is the ION that forms that causes the characteristics of the
acid or base, not the actual acid or base. So, keeping this
in mind, it is the number of these ions that affect
the properties of the solution that the acid or
base is dissolved in. One method to determine
how concentrated a solution is would be to check the
ability to conduct electricity.
IONS AND ELECTRICITY
Ions must be present for electricity to flow. Pure
water has no ions and therefore will not conduct
electricity. If an acid or base is dissolved in pure
water, the degree to which it is dissolved can be
determined by how much electricity is conducted.
The more a substance dissolves AND
DISSOCIATES (forms ions), the more electricity
is conducted. These substances are called
ELECTROLYTES.
pH
pH refers to “power of Hydrogen”. It is a
mathematical calculation of the negative logarithm
of the hydronium ion concentration:
pH = -log[H3O] Since this is an
overview course, we will never calculate
pH.
pH Scale
pH is a scale used to measure
the concentration of the
hydronium ion. A pH of 7
is NEUTRAL. A pH less
than 7 is ACIDIC. Greater
than 7 is BASIC. Since it is
logarithmic, you need to
remember that a pH of 5 is
10 TIMES GREATER
THAN A pH of 6.
INDICATORS
Indicators are chemicals that are used to
test for the presence of other
chemicals by color changes. With acid
base chemistry most people think of
LITMUS. In Acid, LITMUS turns
RED. In Base, LITMUS turns BLUE.
PHTH and Congo Red
We will use two other indicators in lab,
PHENOLTHTHALEIN (PHTH) and
Congo Red. PHTH will be used to test for
Base. In the presence of OH Base, PHTH
will turn a pink color. The more intense
the PINK, the more OH is present. Congo
Red tests for Acid. In the presence of an
acid, it will turn dark blue.
Indicators vs. pH Meters
Indicators will not be as accurate as pH meters since
the Hydronium or Hydroxide ion must be present for
the indicator to react. Therefore, when you see a
color change, you know that the pH of the solution
is NOT a pH of 7 but actually a bit above or below
depending on the indicator used.
ACIDIC RAIN vs. ACID RAIN
There is a difference between acidic rain and acid rain.
All rain is acidic. This is because there is carbon
dioxide in the atmosphere. This carbon dioxide
combines with water to form CARBONIC ACID.
CO2 + H2O  H2CO3
Carbonic acid formation is why soft drink companies
add carbon dioxide to soda. It actually flavors the
drink. A flat soda will taste sweeter.
Carbonic Acid
CO2 + H2O  H2CO3
Carbonic acid is not a very strong acid and easily
breaks down into carbon dioxide and water. It is
the reason that carbon dioxide is added to sodas.
When the carbon dioxide forms carbonic acid, it
gives a slight acidic flavoring to the drink. This is
why a “flat” soda will taste different than a
carbonated beverage.
Testing for CO2
The fact that carbon dioxide combines with water to
form carbonic acid should bring back memories.
Remember testing for carbon dioxide with phenol red?
Remember how it took a short time for the color to
change? Phenol red actually tests for ACID.
So what does that mean?
Carbonic acid will cause rain water to have a natural pH between 5
– 7. When other factors react to lower the pH of rain below a
pH of 5, such as nitrates and sulfates, then rain is considered
to be ACID RAIN.
When rain water is acidic is has dire effects on the ecosystem as well
as leaching toxic metals from the soil. This indirectly affects you
as some of the metals include Al, which has dire effects on the
body.
Carbonic Acid Blood
Carbonic acid also builds up in your blood as well.
When this happens you automatically have built in
buffering systems to keep the pH of your blood at a
constant pH level of about 7.3 – 7.4. (Your body
makes bicarbonates). This is also the reason that you
cannot hold your breath indefinitely. You have to
exhale the Carbon Dioxide.
Where does the CO2 go?
Atmospheric CO2 is increasing, but not at the rate that
is consistent with its production. So where is it
going? The answer is the ocean. The ocean is acting
as a giant “sink” that is absorbing excess CO2. The
problem is that we are producing it faster than the
ocean can absorb it.
NITRATES AND SULFATES
Nitrates and Sulfates, like carbon dioxide, react with
water in the atmosphere to form NITRIC ACID and
SULFURIC ACID.
These acids, in conjunction with the carbonic acid,
cause the pH of rain to drop well below a pH of 5.
When this happens a domino effect of negative
consequences begin to occur to the ecosystem.
Antacids vs. Base
Antacids are typically bases that neutralize acids inside
your stomach. Typically, the stomach pH is between
2 or 3. When it drops below this, people may
experience acid indigestion. Antacids do not
necessarily raise stomach pH to 7, they just increase it
from below 2 to between 2 or 3. You do not want a
pH of 7 in your stomach.
Effects of Metals
There are four primary metals that accompany base
ions with antacid products. Each metal has specific
affects on the body. These metals are as follows
Na-sodium
Ca-calcium
Mg-magnesium
Al-aluminum
Sodium-Na
Sodium is an essential element for the proper
functioning of the body. It helps to maintain proper
fluid levels, assist in nerve impulses, and helps
muscles contract and relax. Your kidneys regulate
your sodium levels. People who have difficulty
regulating sodium will begin to retain more fluids.
This elevates blood pressure as well as increases
blood volume, making the heart work harder.
HIGH SODIUM FOODS/
Can the Cans
Canned and pre-packed foods tend to be higher in sodium than
their fresh counterparts. This is especially true of soups, frozen
dinners and other convenience foods, as well as dehydrated
powders for making sauces and salad dressings. Other foods high
in sodium include:
Soy sauce
Catsup
Worcestershire sauce
Chili sauce
Mustard
Pickles and relishes
Olives
Processed cheese and cheese spread
Baking powder, baking soda and most baked goods, which contain
these ingredients
Canned or frozen vegetables in sauce
Monosodium glutamate (MSG)
Frankfurters, cured ham, sausages and luncheon meats
Salted nuts, chips and other snack foods
Any food additive with the word "sodium" (sodium benzoate, a
preservative; sodium phosphate, an emulsifier and stabilizer)
Ca-Calcium
Calcium is one of the most essential elements in the
body as it is used in bones, teeth, soft tissues, and
many metabolic processes. It regulates permeability
of cells as well as clotting of blood, muscle
contractions, and nerve functions. Calcium helps to
regulate blood pressure.
Foods rich in Calcium
Serving size
Calcium per serving
(mg)*
1 cup
1 oz (slice)
1 cup
1 oz (slice)
290-300
250-270
240-400
165-200
Ice cream or frozen dessert
1/2 cup
90-100
Cottage cheese
Parmesan cheese
Powdered nonfat milk
1/2 cup
1 Tbs
1 tsp
80-100
70
50
Food with Calcium
Dairy products
Milk†
Swiss cheese
Yogurt
American cheese
Sardines in oil (with bones)
3 oz
Canned salmon (with bones) 3 oz
Broccoli
Soybean curd (tofu)
Turnip greens
Kale
Corn bread
Egg
1 cup
4 oz
1/2 cup,
cooked
1/2 cup,
cooked
2 1/2-in.
square
1 medium
370
170-210
160-180
145-155
100-125
90-100
80-90
55
Mg-Magnesium
Magnesium is the second most common mineral in the
body, behind calcium. Most is found in the bones
and muscles (86%) while the rest is found in the
brain, heart, liver, kidney, and blood. Mg is used in
over 300 enzyme reactions of the body. It is used to
synthesize nucleic acids, proteins, relax muscles,
prevent kidney stones, and helps prevent diabetes.
Mg is also used to help regulate blood pressure.
Whole food sources of Magnesium
Whole Food Sources
Serving
Magnesium (mg)
Brown rice, cooked
1 cup
83.8
Almonds, raw
1 ounce
81.1
Spinach, cooked
1/2 cup
78.3
Swiss chard, cooked
1/2 cup
75.2
Lima beans, cooked
1/2 cup
62.9
Avocado
Peanuts*, raw
Hazelnuts, raw
Okra, cooked
1 large
1 ounce
1 ounce
1/2 cup
50.0
49.8
49.0
45.6
Black-eyed peas, cooked
1/2 cup
42.8
Aluminum
Aluminum has no role in the human body. As of this
time, there are no known organisms that use
aluminum in any of their biological processes. It is
toxic to all living creatures. Aluminum has been
linked to the following: Alzheimer’s, Parkinson’s,
liver disease, cancers, heart problems, bone disorders,
infection, memory loss, speech disorders, kidney
disorders, and the list goes on. It is estimated that
the average person takes in approximately between 3
and 10 mg of Al per day.
Sources of Al
Al can be absorbed into the body through the digestive tract,
the lungs and the skin, and is also absorbed by and
accumulates in the bodies tissues. Aluminum is found
naturally in our air, water and soil. It is also used in the
process of making cooking pots and pans, utensils and
foil. Other items such as over the counter pain killers,
anti-inflammatory products, can also contain aluminum.
Aluminum is also an additive in most baking powders, is
used in food processing, and is present in antiperspirants,
toothpaste, dental amalgams, bleached flour, and grated
cheese. One of the biggest source of aluminum,
however, comes from our municipal water supplies.
Products containing Al
•
THE FOLLOWING PRODUCTS MAY CONTAIN ALUMINUM-Check the label:
Foods made with aluminized baking powder*, self-rising flour*, and salt. The following are some of these products:
Microwave popcorn
Salted snacks
Hot cocoa mixes
Coffee creamers
Pickles and relish
*Flour tortillas
*Pizza crust
*Muffins
*Doughnuts
*Cookies
*Pancakes
*Waffles
*Cupcakes
*Cakes
*Baking mixes
*Brownies
*Pastries
*Corn bread
*Banana bread
*Carrot bread
*Dipping batter for fried foods
Products containing Al
• Antiperspirents
Many body lotions and creams
Most cosmetics
Shampoos and conditioners
Soaps
Suntan lotions
Lip Balm
Etc.