Unit 12: Acids and bases
 Types
o Arrhenius acids and bases

H+ and OH
pH
o Indicators

Neutralization

Titration reactions
o Bronsted-Lowery acids and bases

Date
Proton donor and proton accepter (NH3 and NH4+)
Topic
Homework (Due at the beginning of the next
period)
Acids, Bases and their
properties
Read next topic; 2)Indicators + 3)pH.
Do the practice
Indicators and pH
Read next topic 4)Acid and Base Neutralization,
Do the practice
Acids, bases and indicators
lab
Acids, bsaes and indicators
lab
Finish the lab (due 2 days later)
Acid-Base Neutralization
Titration practice
Read the next topic; 5) Bronsted-lowry
Do the practice
Titration lab
Titration lab
Finish the lab (due 2 days later)
Bronsted-Lowry Acids and
bases
Do the review problems and study for the test
Review
Study for the test
Test
1) Properties of Arrhenius Acids and Bases: Which is more dangerous; an acid or
base?
OH MY GOD! ITS AN ACID!!! Why are acids scary? Why are they ‘scarier’ than bases? Should
they be?
Acids and bases are a cornerstone of chemistry. These two substances have uses in industry,
medicine, geology, cosmetics and in the home as well. Ammonia (NH4OH) is a base that is used
to clean grease buildup on floors. Hydrochloric acid (HCl) is used to partially dissolve the
surface of concrete flooring so that it roughens to hold floor paint better. Hydrofluoric acid
(HF) is used to etch glass. Sulfuric acid (H2SO4) is used as a catalyst for certain reactions,
and as a reactant in refining iron ore. Sodium hydroxide (NaOH) is reacted with animal fat or
vegetable oil to form soap, and it is also used for drain cleaner.
There are two ways that we will talk about to define what an acid and a base are. The first
definition we will address is that for Arrhenius Acids and bases. Arrhenius acids are substances
that contain H+ ions that ionize when dissolved in water and Arrhenius bases produce OH- ions
when dissolved in an aqueous solution.
a) Acids
Acids are the only molecules that ionize when
dissolved in water. Acids are electrolytes, unlike
other molecular substances like water (H2O) and
sugar (C6H12O6). The H leaves the acid and bonds to
the water molecule to form a hydronium ion (H3O+).
Examples of these acids include:
-
HCl (g) + H2O (l)  H3O+ (aq) + Cl- (aq)
o The acid HCl contains 1 H+ which combines
with H2O to form H3O+
-
H2SO4 (l) + 2 H2O (l)  2 H3O+ (aq) + SO4-2 (aq)
o The acid H2SO4 contains 2 H+ which
combines with 2 H2O to form 2 H3O+
i.
Properties of acids
1) Acids eat away (oxidize) active metals (above H2 on table J)
This is probably what you think of when you hear the word acid, some sort of liquid eating away
at a metal like the blood of the extra-terrestrials in the movie Alien. There is actually some
truth to this idea. The hydrogen in the acid will cause the oxidation of metals and produce
hydrogen gas in the process.
For example: Mg + HCl  MgCl2 + H2
This is actually a reaction you performed in the types of reactions lab. You then tested it with a
flaming splint and saw that the gas produced was flammable, since it was hydrogen gas.
2) Acids have a pH less than 7
You may be familiar with the pH scale from previous science classes. A pH below seven is
considered to be acidic, greater than seven basic (or alkaline), and 7 is neutral. pH actually
measures the concentration of H+ ions in a solution, and a change in a pH of 1 is a ten times
difference. Something with a pH of 2 is 10x more acidic than something with a pH of 3, and it is
100x more acidic than something with a pH of 4…We’ll get more into this later
3) Acids solutions conduct electricity
Remember, in order for something to conduct there needs to be mobile charges present. When
an acid is add to water it creates H+ ions and some other anion that can move about freely, since
they are dissolved in a solution. This means it will conduct, and is considered an electrolyte (the
same is true for bases)
4) Dilute solutions of acids taste sour
Do you like sour candies? How about Warheads? What these
candies have in common is the presence of dilute acids, often
citric acid. These solutions taste sour and are some of my
favorites. With that said, DO NOT TASTE ANY ACIDS IN LAB,
or you may very well be the next Darwin Award winner.
5) Acids react with carbonates to form CO2, salt and water vapor
Baking soda and vinegar: NaHCO3 (s) + HC2H3O2 (aq)  CO2 (g) + H2O (l) + NaC2H3O2 (aq)
This is the “volcano” reaction…the CO2 gas given off causes the solution to foam up and out.
6) Acids can be formed by reaction of gaseous oxides with water
This is where acid rain comes into play. Water passes through NO2 or SO2 in the air and forms
weak acids that can cause environmental problems.
ii. Properties of Bases
1) Bases have a pH greater than 7
As stated previous for acids, anything greater than pH of 7 is basic, and a change in 1 pH is a
ten times change in concentration of OH- ions. Something with a pH of 13 is 100x more basic
than a pH of 11.
2) Basic solutions conduct electricity
Since bases produce OH- ions in solution, these free and mobile charges can conduct electricity.
Since they conduct, they are also known as electrolytes
3) Bases taste bitter
Some medicines, baking soda, drain-o are all basic and would taste bitter. Again, do not become
the newest Darwin Awardee, do not go around tasting these things.
4) Bases can be formed when groups 1 and group 2 metals react with water
Remember those cool videos of throwing sodium into water and the explosion that followed.
What happened was the sodium was reacting with the water to produce hydrogen gas (the
boom), sodium hydroxide (the base) and heat.
5) Bases hydrolyze fats (turns them into soap, a.k.a., saponification)
A pretty neat feature of bases is that they turn fat into soap. Drain cleaner
works by converting the grease that is clogging your drains into soap, which
then can be washed away by the water pressure of the backed up sink. If you
have ever seen ‘Fight Club’ they use other sources of fat to make soap. This is
really where the dangers of bases lie. Accidently get some on your skin, you may
not even feel it right away, it will start to eat at your flesh. You skin may start to feel silky, as
the fats in the oils on your skin, as well as your flesh, are slowly turned into soap. Make sure to
rinse off your hands and such after working with bases 
pH of Common Substances
Apples
Orange Juice
Grapes
Carrots
Seawater
Soap
Milk of Magnesia antacid
Household ammonia
Household bleach
pH
About 3
3
About 4
About 5
8-9
9-10
10
11
12
1) Properties of Arrhenius Acids and Bases Practice
A) Short-Answer
1) Name a metal that can react with an acid:_______________________________
2) Give a pH value that indicates an alkaline solution:__________________________
3) When on compound dissolves in water, the only positive ion produced in the solution is
H3O+(aq). This compound is classified as ________________
4) which of the following substances is an Arrhenius Acid:
a) H3PO4
b) Ba(OH)2
c) CH3COOCH3
d) NaCl
5) Why does HCl (aq) conduct electricity while C6H12O6 (aq) cannot? Explain in terms of
ionization.
B) Identify each as an acid or base based on their formulas and properties.
Property
Acid or
Base?
Property
Turns litmus red
Produces OH- in solution
Tastes sour
Tastes bitter
Hydrolyzes fats into soap
HCl (aq)
Reacts with active metals
to form H2
KOH (aq)
pH of 12
Forms H3O+ in water
Acid or
Base?
2) Indicators: How do we know if a solution is acidic or basic?
Kind of an important question when you think about it. ‘Will that stuff turn my flesh into soap or
simply eat a whole in it?’ More seriously, if that were to spill, how should I clean it up?
a) pH probes
These are electrical probes that detects the conductivity of the solution and needs to be
calibrated by giving it a ‘taste’ of two different solutions with different pH’s. Sounds
pretty tedious right? That’s why we won’t use them in class.
b) Acid-Base indicators
These are substances who’s colors are sensitive
to the pH of the solution they are in. For
example, for methyl orange in a solution with a pH
less than 3.2 would be red. If it was in a solution
with a pH greater than 4.4 it would be yellow. If
it was in a solution between 3.2 and 4.4 it would
be orange! This information can be found on
Table M, which lists common indicators which we
will use in lab. If the pH is less than the lower
number, it will be the color listed on the left. If
it is greater than the larger number, it will be the color on the right. If it is in between
the two numbers, it will be in between the two colors (usually). Each indicator, when used
alone, only will give us qualitative information. It will tell us if it is greater than, less than,
or in between two pH’s and no the actual pH.
3) What is pH pH = Power of Hydronium Ion In A Solution
Ah, pH. It’s the easiest method to use for comparing the strengths of acids and bases. We
test our fishtanks (fish pee out ammonia, which is a base, and brings the pH up), our lawns (acid
rain brings the pH of the soil down) and even food is pH tested as it is being made to make sure
that it falls within the right range. You wouldn’t want your super-sour candy to have too little
bite, would you? So just what is this pH, what does it mean, and how is it measured?
Water normally breaks up very slightly to form hydrogen ions and hydroxide ions:
H2O  H+1 + OH-1
In neutral water, the concentration of H+ = 1.0 X 10-7 M, so the pH = 7 and we call that neutral.
ADDING ACIDS TO WATER- adding an acid to water increases the H3O+ concentration, so
that the pH increases by 1 as the acid strength increases tenfold.
When the concentration of H+ = 10-1 M, the pH = 1
When the concentration of H+ = 10-2, the pH = 2
When the concentration of H+ = 10-3, the pH = 3
When the concentration of H+ = 10-4, the pH = 4
A solution with a pH of 1 is 10 times more acidic than a solution with a pH of 2.
A solution with a pH of 1 is 100 times more acidic than a solution with a pH of 3.
A solution with a pH of 1 is a 1000 times more acidic than a solution with a pH of 4.
ADDING BASES TO WATER- adding a base to water decreases the H30+ concentration, so
that the pH decreases by one as the base strength increases tenfold.
When the concentration of OH- = 10-1 M, the pH = 13
When the concentration of OH- = 10-2, the pH = 12
When the concentration of OH- = 10-3, the pH = 11
When the concentration of OH- = 10-4, the pH = 10
A solution with a pH of 13 is 10 times more basic than a solution with a pH of 12.
pH Practice
A) Multiple Choice Questions: Place your answer in the space in front of each question.
_____1) Which of the following solution pH values is the most acidic?
a) 5
b) 7
c) 9
d) 11
_____2) A pH of 14 is how many times more basic than a pH of 12?
a) 10 times
b) 100 times
c) 1000 times
d) 10000 times
_____3) Which of the following solutions can have a pH of 5?
a) a 10-5 M solution of HCl
b) a 10-5 M solution of NaOH
-5
c) a 10 M solution of NaCl
d) a 10-5 M solution of CH4
_____4) What is the pH of a solution formed when equal volumes of 0.1 M HCl and 0.1 M NaOH are
added to a beaker?
a) less than 7
b) more than 7
c) exactly 7
_____5) Strong acids and bases have more dissolved ions per liter than weak acids and bases.
Which pH value indicates the solution that is an acid that conducts electricity the best?
a) 3
b) 5
c) 9
d) 12
_____6) Which pH value indicates the solution that is a base that conducts electricity the poorest?
a) 3
b) 5
c) 9
d) 12
B) Short-Answer: please place your answers in the provided spaces.
1) A pH of 4 is how many times more acidic than a pH of 6?_________________________
2) A pH of 11 is how many times more basic than a pH of 8?_________________________
3) Complete the following Chart:
Indicator used
pH of solution
Methyl orange
Litmus
Bromcresol green
Thymol blue
9
10
2
13
Color of indicator in
solution
Is the solution an aci
4) Explain why methyl orange would be a poor choice of indicator to use if you were testing to see if a
solution was definitively an acid or a base.
4) Acid and Base Neutralization: What happens when we mix Acids and Bases?
Neutralization occurs when acidic and basic solutions mix. ‘Neutral’ meaning a neutral pH
of 7, and ‘ization’ meaning ‘the process of’. We are making the solution neutral! This happens
because when acids mix with bases the H+ ions combine with the OH- ions to produce H(OH), or
the more familiar way of writing it, H2O. The cation from the base and the anion from the acid
also combine to give us a salt. It’s basically a double replacement reaction, which you have seen
before:
HCl (aq) + NaOH (aq)  NaCl (aq) + HOH (l)
Acid
Base
Salt
Water
H2SO4 (aq) + 2 KOH (aq)  K2SO4 (aq) + 2 HOH (l)
Acid
Base
Salt
Water
It takes one mole of H+ ions to neutralize one mole of OH- ions. It is this simple fact that
allows us to calculate how much acid (or base) we need to completely neutralize the other. This
process of controlled acid-base neutralization is called titration. The equation to solve for
titration problems is:
# H MaVa = # OH MbVb
Where #H is the number of H+ released by the acid (HCl would give 1, H2SO4 would give
2, etc..), Ma is the molarity of the acid, Va is the volume of the acid and the same applies to the
other side of the equation for the bases. It may help to examine what is going on in the equation
in order to understand what is going on.
When you multiply the molarity of the acid by the volume of the acid (MaVa) you get the
number of moles of the acid. The same applies to the base:
# H Molesa = # OH Molesb
Now we need to factor in how many H+’s are released by the acid. Something like HCl only
has one H+ to release, where as something like H3PO4 would have 3 H+’s to release. When you
multiply the #H by the number of moles you get the moles of H+ (and moles of OH - on the other
side) which would simplify to:
Moles H+ = Moles OHThis happens in a neutral solution. A fun way to remember the original formula (# H MaVa
= # OH MbVb) is to say it aloud, which goes something like this: MAH-VAH equals MUB-VUB.
Performing a titration
Problem - You find a bottle labeled "NaOH", with no
concentration written on it. You want to find out the
concentration, because unless the concentration is known,
this sample is totally useless in the lab. How can this be
done?
1) Put a certain volume of the base in a buret
2) Place a certain volume of standardized
solution acid with some phenolphthalein
indicator into an Erlenmeyer flask.
3) Add the base to the acid drop-wise until the
indicator just begins to turn color.
4) Record the volume of base necessary to neutralize the acid.
The point where the indicator turns color is called the "endpoint". Because the indicator
might not turn color at exactly pH = 7, it might be a little off from the equivalence point, or the
point where all of the acid H+ ions might have in fact reacted with all of the base OH- ions.
The best way to do a titration is to use a pH meter.
ENDPOINT: The pH at which an indicator that has been added to a titration setup turns color.
Phenolphthalein turns from colorless to pink at a pH of 8.2,
which is slightly on the base side of neutral. When base is added to
acid with phenolphthalein in it, the solution will gradually take longer
to get the pink color out of until one drop of base turns the solution
permanently pink. This will be a pH or 8.2. This is the endpoint.
EQUIVALENCE POINT: The point at which the titrated solution
has a pH of 7. The concentration of hydronium is equivalent to the
concentration of hydroxide. This can be determined by using a pH
probe to determine when the solution is neutral rather than an
indicator.
The best indicators give an endpoint close to the equivalence point. To determine if a
solution has been neutralized, choose an indicator that changes color closest to a pH of 7.
Phenolphthalein is the most commonly used indicator for titration, though bromthymol blue does
a nice job as well. If you really have the big bucks, buy a pH probe…just stop titrating when the
pH reaches 7!
Sample Problems:
How many moles of LiOH are needed to exactly neutralize 2.0 moles of H 2SO4?
Since we are given moles of both acid and base, use the equation # H Molesa = # OH Molesb.
# H Molesa = # OH Molesb, rearranged to solve for moles of base is Moles b = # H Molesa / # OH
Molesb = # H Molesa / # OH = (2 X 2.0 moles) / 1 = 4.0 moles of LiOH
How many moles of H2SO4 are needed to exactly neutralize 5.0 moles of NaOH?
Since we are given moles of both acid and base, use the equation # H Moles a = # OH Molesb.
# H Molesa = # OH Molesb, rearranged to solve for moles of acid is Moles a = # OH Molesb / # H
# OH Molesb / # H = (1 X 5.0 moles) / 2 = 2.5 moles of H2SO4
If it takes 15.0 mL of 0.40 M NaOH to neutralize 5.0 mL of HCl, what is the molar concentration of the HCl
solution?
Since we are given molarity and volume for both acid and base, use the equation # H MaVa = # OH MbVb
# H MaVa = # OH MbVb, rearranged to solve for molarity of acid is Ma = # OH MbVb / # H Va
Ma = # OH MbVb / # H Va = [(1) (0.40 M) (15.0 mL)] / [(1) (5.0 mL)] = 1.2 M HCl
If it takes 10.0 mL of 2.0 M H2SO4 to neutralize 30.0 mL of KOH, what is the molar concentration of the KOH?
Since we are given molarity and volume for both acid and base, use the equation # H MaVa = # OH MbVb
# H MaVa = # OH MbVb, rearranged to solve for molarity of base is M b = # H MaVa / # OH Vb
Mb = # H MaVa / # OH Vb = [(2) (2.0 M) (10.0 mL)] / [(1) (30.0 mL)] = 1.3 M KOH
How many mL of 2.0 M H2SO4 are required to neutralize 30.0 mL of 1.0 M NaOH?
Since we are given molarity and volume for both acid and base, use the equation # H MaVa = # OH MbVb
# H MaVa = # OH MbVb, rearranged to solve for volume of acid is Va = # OH MbVb / # H Ma
Va = # OH MbVb / # H Ma = [(1) (1.0 M) (30.0 mL)] / [(2) (2.0 M)] = 7.5 mL H2SO4
Neutralization practice:
A) Write the formula of the salt formed in each reaction:
1) H2SO4 (aq) + Mg(OH)2 (aq)  2 HOH + _________________
2) H3PO4 (aq) + 3 NaOH (aq)  3 HOH + __________________
B) Write the formula of the acid used in each reaction and then balance the reaction:
1) ______________________ (aq) + ____ Al(OH)3 (aq)  ____ HOH (l) + ____ Al2(SO4)3 (aq)
2) _____________________ (aq) + ____ Ba(OH)2 (aq)  ____ HOH (l) + ____ Ba(C2H3O2)2 (aq)
C) Write the formula of each base used in each reaction and then balance the reaction:
8) ____ H2SO3 (aq) + __________________ (aq)  ____ HOH (l) + ____ MgSO3 (aq)
9) ____ H3PO4 (aq) + __________________ (aq)  ____ HOH (l) + ____ Ca3(PO4)2 (aq)
D) Solve the following titration problems:
1) How many moles of KOH are needed to neutralize 1.5 moles of H2SO4?
2) What volume of 0.80 M HCl will exactly neutralize 100. mL of 0.40 M KOH?
3) What is the molarity of an H2CO3 solution if it takes 50. mL of H2CO3 to exactly neutralize
100. mL of 0.50 M NaOH?
4) 50. mL of H2SO4 of unknown concentration is titrated with 25 mL of 5.0 M NaOH. What is
the molarity of the H2SO4?
5) How many moles of H2SO4 can be neutralized by 0.10 L of 0.50 M NaOH?
1)3.0 moles 2)50.mL 3)0.50M 4)1.3M 5).025 moles
5) Bronsted-Lowry Acids and Bases If all poodles are dogs, are all dogs poodles?
Over the course of the last few topics, we have focused on acids and bases as discovered
by Svante Arrhenius. There are other theories on what acids and bases are. One theory,
developed by Johannes Brönsted and Thomas Lowry (published separately, but within months of
each other, so they both got credit), is more general in nature. All poodles are dogs, but not all
dogs are poodles. The Arrhenius theory is the “poodle” theory, and the alternate theory is the
“dog” theory.
According to Svante Arrhenius:
Acid – a compound that dissolves in water to produce H+1 as the only positively charged
ion in solution
Base – a compound that dissolves in water to produce OH-1 as the only negatively charged
ion in solution
According to this alternate theory put forth by Johannes Brönsted and Thomas Lowry:
Acid - a proton (H+) donor
Base - a proton (H+) acceptor
H+ is a proton. Think about the hydrogen atom. It’s made of one proton with an electron
zipping around at a distance. How does H become H+1? By removing that one and only electron,
leaving a proton. A “naked” proton. According to this theory, an acid is a substance that gives
up an H+ ion to another substance. In this way the two theories are the same, but define acids
as a substance that ‘donates’ a H+, also known as a proton.
According to this theory, a base is a substance that takes an H+ ion from another
substance. This is a more general definition, which also includes Arrhenius bases. For example:
HCl + NaOH  NaCl + H2O
Acid Base
HCl is a proton donor, and the NaOH is the proton acceptor. This is a ‘poodle’ example, it
is both Arrhenius and Bronsted-Lowry. Here are some other examples:
HCl + H2O  H3O+ + ClAcid Base
The HCl gives its H+ to the H2O
NH3 + H2O  NH4+ + OHBase Acid
The H2O gives is H+ to the NH3
This visualization might help:
The HCl loses its H+1 to H2O.
HCl is the acid in this reaction
because it lost (donated) a proton
(H+1)
H2O is the base in this reaction
because it gained (accepted) a
proton (H+1)
The H2O loses its H+1 to NH3.
H2O is the acid in this reaction
because it lost (donated) a proton
(H+1)
NH3 is the base in this reaction
because it gained (accepted) a
proton (H+1)
The HC2H3O2 loses its H+1 to H2O.
HC2H3O2 is the acid in this reaction
because it lost (donated) a proton
(H+1)
H2O is the base in this reaction
because it gained (accepted) a
proton (H+1)
5) Bronsted-Lowry Definition of Acids and Bases Practice
A) For each of the following systems, identify the Bronsted/Lowry acids and bases by writing A for the acid and B
for the base on the reactant side:
1.
HBr +
H2O <====> H3O+
2.
H2O +
H2O <====>
H3O+ +
3.
NH3 +
OH- <====>
NH2-
4.
H2O +
HPO42-
5.
H3PO4
6.
CH3COO- +
H3O+
7.
H2PO4-
+
CH3COO- <====>
8.
H2O +
S2-
<====>
9.
CN- +
HCH3COO <====>
10.
OH- +
NH4+
+
Br-
+
OH-
+
H2O
PO43-
<====>
H2PO4-
H2O <====>
<====>
HS-
+
H3O+
+
HCH3COO
+
OH-
+
CH3COO-
H2O
H2O
HPO42-
HCH3COO +
HCN
<====>
H3O+
+
+
NH3