Toxins Unit
Investigation IV:
Neutralizing Toxins
Lesson 1: Heartburn
Lesson 2: Watered Down
Lesson 3: pHooey!
Lesson 4: Proton Shuffle
Lesson 5: Neutral Territory
Lesson 6: Drip Drop
Lesson 7: Call Poison Control
Toxins Unit – Investigation IV
Lesson 1:
Heartburn
ChemCatalyst
Countless products are advertised on TV
with the promise of reducing acid
indigestion.
• What is acid indigestion? What is
acidity?
• What does acid have to do with your
stomach?
• How do you think acid “reducers”
work?
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
The Big Question
• What are some characteristics of
solutions that are acidic, basic, or
neutral?
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
You will be able to:
Describe the differences among acidic,
basic, and neutral solutions.
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
Notes
• Indicators: A set of substances that
respond to other substances with vivid
color changes.
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
Activity
Purpose: This activity will introduce you
to a special category of solution.
(cont.)
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
(cont.)
Safety note: Do not get acids and
bases on your skin. In case of a spill,
rinse with large amounts of water.
Wear goggles.
(cont.)
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
Substance
table salt (aq)
Formula
NaCl
vinegar (aq)
C2H4O2
rubbing alcohol
C3H8O
ammonium
hydroxide (aq)
distilled water
NH4OH
stomach acid (aq)
washing soda
(aq)
lemon juice
drain cleaner (aq)
Cabbage Indicator Indicator
Juice
color
number
H2O
HCl
Na2CO3
C6H8O7
NaOH
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
(cont.)
0
7
14
(cont.)
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
(cont.)
Observations when added to CaCO3
water
stomach acid
vinegar
drain cleaner
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
Making Sense
• Look for patterns in the names,
chemical formulas, uses, and
properties of the substances you
tested.
• List four characteristics of acids.
• List four characteristics of bases.
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
Notes
Indicators can be used to identify substances that are
acidic, basic, and neutral when dissolved in water.
• Acids turn cabbage juice pink and are between 0
and 7 on the universal indicator scale.
• Bases turn cabbage juice green or blue and are
between 7 and 14 on the universal indicator scale.
• Neutral substances do not change color with
cabbage juice and are at or very near 7 on the
universal indicator scale.
(cont.)
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
(cont.)
• pH scale: A number line from 0 to 14.
The numbers are associated with
indicator colors.
• The numbers associated with indicator
colors are also called pH numbers or
simply pH.
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
Check-In
• An unknown substance is purple with
cabbage juice and does not react with
calcium carbonate. Is it an acid, base
or neutral substance? Explain.
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
Wrap-Up
• Acids and bases are different types of
solutions and are classified according
to their observable behavior.
• Acids and bases respond differently to
indicators. Depending on the indicator,
different colors will form that show
either an acidic or basic substance.
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
Toxins Unit – Investigation IV
Lesson 2:
Watered Down
ChemCatalyst
• Describe what you observe in the three
vials.
• What is one explanation for the
differences you observe?
• If you tested each solution with
universal indicator before putting in the
gummy bears, what colors would you
expect to see?
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
The Big Question
• How does dilution affect the acidity or
basicity of a solution?
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
You will be able to:
Explain how dilution affects the
concentration and pH of a solution.
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
Activity
Purpose: In this activity you will
examine the effect of concentration on
acidity and basicity of solutions.
(cont.)
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
(cont.)
Safety note – Do not get acids and
bases on your skin. In case of a spill,
rinse with large amounts of water.
Wear goggles.
(cont.)
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
Data Table for dilution of 1.0 M HCl
Well # Concentration
1.0 M HCl
Color
pH number
0.10 M HCl
0.010 M HCl
0.0010 M HCl
0.00010 M HCl
0.000010 M HCl
0.0000010 M HCl
0.00000010 M HCl
0.000000010 M HCl
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
Data Table for dilution of 1.0 M NaOH
Well # Concentration
1.0 M NaOH
Color
pH number
0.10 M NaOH
0.010 M NaOH
0.0010 M NaOH
0.00010 M NaOH
0.000010 M NaOH
0.0000010 M NaOH
0.00000010 M NaOH
0.000000010 M NaOH
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
Data Table for dilution of 1.0 M NaCl
Well # Concentration
Color
pH number
1.0 M NaCl
0.10 M NaCl
0.010 M NaCl
0.0010 M NaCl
0.00010 M NaCl
0.000010 M NaCl
0.0000010 M NaCl
0.00000010 M NaCl
0.000000010 M NaCl
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
Making Sense
• What does concentration have to do
with the acidity or basicity of a
solution?
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
Notes
0
7
14
More OH–
More H+
pH scale
(cont.)
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
(cont.)
Arrhenius definition:
• An acid is any substance that adds a
hydrogen ion (H+) to the solution.
• A base is any substance that adds a
hydroxide ion (OH–) to the solution.
(cont.)
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
(cont.)
HA  H+ + A–
XOH  X+ + OH–
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
Check-In
• Lemon juice has a pH of about 2. What
does this tell you about what is in the
solution?
• What would happen if you diluted this
solution?
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
Wrap-Up
• The acidity and basicity of a solution
are related to the concentration of the
solution. Dilute solutions are less
acidic and basic than more
concentrated solutions.
• Dilution of an acid or a base results in
a solution that is increasingly neutral.
(cont.)
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
• The pH scale is related to the
concentration of H+ and OH– ions in
solution.
• According to Arrhenius, an acid is any
substance that adds a hydrogen ion
(H+) to the solution and a base is any
substance that adds a hydroxide ion
(OH–) to the solution.
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
Toxins Unit – Investigation IV
Lesson 3:
pHooey!
ChemCatalyst
Examine the following data:
Substance
0.10 M HCl
0.010 M HCl
0.0010 M HCl
1.0 M NaOH
0.10 M NaOH
0.010 M NaOH
Water
pH
1.0
2.0
3.0
14.0
13.0
12.0
7.0
(cont.)
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
(cont.)
• What do you think pH really
represents?
• How does the concentration of the
solutions relate mathematically to the
pH of the solutions?
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
The Big Question
• How does pH relate to the
concentrations of acidic and basic
solutions?
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
You will be able to:
Find the pH of a solution if you know the
concentrations of hydrogen or hydroxide
ions that it contains.
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
Activity
Purpose: You will explore the
relationship between pH, pOH, [H+], and
[OH–].
(cont.)
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
Substance
Acidic pH
or
Basic?
[H+]
(in decimal)
[H+]
(in scientific
notation)
1 M HCl
Stomach acid (0.1 M HCl)
Acidic
Clear Soda
Rain Water
3
1.0  10–6 M
7
0.0000001 M
Basic
1 M NaOH
1.0  10–8 M
8
Ammonia
Drain Cleaner (0.1 M
NaOH)
0.0000001M
Neutral
Salt Water
Washing Soda
0.001 M
Acidic
Distilled Water
Alcohol
1.0  10–1 M
0.1 M
0.0000000001 M
1.0  10–10 M
13
1.0  10-14 M
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
Well
A
HCl
B
C
D
E
F
G
H
I
pH
1
2
3
4
5
6
7
7
7
[H+]
1.0  10–1 M
[OH–]
pOH
13
1.0  10–2 M 1.0  10–12 M
1.0  10–3 M
1.0  10-4 M 1.0  10–10 M
1.0  10–5 M
1.0  10–6 M
1.0  10–7 M
1.0  10–7 M 1.0  10–7 M
1.0  10–7 M
12
10
7
7
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
NaOH
Well
R
Q
P
O
N
M
L
K
pH
7
7
7
8
9
10
11
12
[H+]
[OH–]
pOH
1.0  10–7 M 1.0  10–7 M
7
1.0  10–7 M
7
1.0  10–7 M
1.0  10–8 M
1.0  10–9 M 1.0  10–5 M
5
1.0 x10–10 M
1.0  10–11 M
3
1.0  10–12 M 1.0  10–2 M
J
13
1.0  10–13 M 1.0  10–1 M
1
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
Making Sense
• How are pH and pOH related to each
other mathematically?
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
Notes
pH = 4
pH = 5
This box
would show
1,000 H+ ions
and 1,000 Cl–
ions.
Key:
pH = 6
pH = 7
This box
would show
100 H+ ions
and 100 Cl–
ions.
H+
(cont.)
Cl–
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
(cont.)
pH = –log[H+]
pOH = –log[OH–]
(cont.)
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
(cont.)
Sample Problem:
• What is the pH of a solution with a
hydrogen ion concentration of
3.4  10–4 moles/ L?
(cont.)
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
(cont.)
Please be careful when entering
scientific notation into your calculator—
it is very easy to make a mistake. When
entering 3.4  10–4, first enter “3.4”.
Then press the button labeled “EXP” or
“10X” or “EE”. Now enter –4, using the
“+/–“ key, not the subtraction key.
Never try to enter this number by
pressing “X” and “10” and “–4”.
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
Check-In
• What is the pH of a solution with
[OH–] = 1.0  10–12 M?
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
Wrap-Up
• The relationship between pH and pOH of a
solution is expressed by the following: pH +
pOH = 14.
• The relationship between [H+] and [OH–] in
a solution is expressed by the following: –
log [H+] + –log [OH–] = 14.
• The pH of a solution is logarithmically
related to the concentration of hydrogen
ion and can be calculated mathematically
using the following equation: pH = log [H+]
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
Toxins Unit – Investigation IV
Lesson 4:
Proton Shuffle
ChemCatalyst
Besides HCl, the digestive system also
produces a compound called
bicarbonate, HCO3–. Bicarbonate plays a
vital role in regulating the pH of the
digestive system.
• Do you think bicarbonate, HCO3–, is an
acidic, basic or neutral substance?
Explain your reasoning.
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
The Big Question
• Is there a better way to classify acids,
bases, and neutral substances?
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
You will be able to:
Explain the behavior of acids and bases
on a molecular level.
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
Activity
Purpose: This activity will provide you
with information to expand on your
definition of acids and bases.
(cont.)
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
(cont.)
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
Making Sense
• The Arrhenius definition of acids and
bases defines them as substances that
release either H+ or OH–. How can we
expand on this definition to include
substances like methylamine, CH3NH2,
and ammonia, NH3?
(cont.)
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
(cont.)
Acids
(cont.)
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
(cont.)
Bases
(cont.)
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
(cont.)
Neutral Substances
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
Notes
Brønsted-Lowry definitions
• An acid is a substance from which a
proton can be removed.
• A base is a substance that can remove
a proton from another substance.
(cont.)
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
(cont.)
H2O (l)  H+(aq) + OH–
(cont.)
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
(cont.)
NH3 (aq) + H2O (l)  NH4+ (aq) + OH–
(aq)
(base)
(acid)
HNO3  H+ + NO3–
HNO3 + H2O  H3O+ + NO3–
(acid) (base)
pH = –log[H3O+]
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
Check-In
• Do you predict a solution of CH4 to be
acidic, basic or neutral? Explain.
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
Wrap-Up
• A Brønsted-Lowry acid is a substance
from which a proton can be removed.
• A Brønsted-Lowry base is a substance
that removes a proton from an acid.
• When an acid reacts with water,
hydronium ion is produced.
• Some substances can act as both acid
and base.
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
Toxins Unit – Investigation IV
Lesson 5:
Neutral Territory
ChemCatalyst
Milk of magnesia, Mg(OH)2, can reduce
excess stomach acid, HCl.
• What products do you think are
produced when Mg(OH)2 and HCl are
mixed?
• What do you think happens when you
add an acid together with a base?
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
The Big Question
• How do acids and bases interact with
each other?
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
You will be able to:
Write balanced chemical equations
describing the interactions between
acids and bases.
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
Activity
Purpose: In this activity, you will
examine the products of reactions
between acids and bases.
(cont.)
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
starting
solution
pH at
start
solution
added
pH after
mixing
acidic, basic,
or neutral
Did a reaction
occur?
Reactions with NaOH
0.10 M HCl
0.10 M
NaOH
0.10 M
HNO3
0.10 M
NaOH
solid
Ca(OH)2

0.10 M
NaOH
Reactions with HCl
0.10 M
NaOH
0.10 M
HCl
0.10 M
HNO3
0.10 M
HCl
solid
Ca(OH)2

0.10 M
HCl
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
Making Sense
Complete the following set of general
equations for the reaction of HCl and
NaOH with the “generic” acid HA and the
“generic” base MOH.
HA + HCl

HA + NaOH 
MOH + HCl

MOH + NaOH 
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
Notes
• A neutralization reaction is a reaction
in which an acid and a base react in
aqueous solution to produce a salt and
water.
(cont.)
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
(cont.)
HA + MOH  MA + H2O
(cont.)
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
(cont.)
2HCl (aq) + Mg(OH)2 
MgCl2 (aq) + 2 H2O (l)
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
Check-In
• Sulfuric acid, H2SO4, reacts with
magnesium hydroxide, Mg(OH)2. Write
a balanced equation for the reaction
that occurs.
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
Wrap-Up
• A neutralization reaction is a reaction
between an acid and a base to
produce a salt and water.
• When acids are mixed with acids, the
pH remains less than 7. When bases
are mixed with bases, the pH remains
greater than 7.
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
Toxins Unit – Investigation IV
Lesson 6:
Drip Drop
ChemCatalyst
A student mixes 100 mL of 0.10 M HCl with
different volumes of 0.10 M NaOH.
A. 100 mL of 0.1 M HCl + 50 mL of 0.1 M
NaOH
B. 100 mL of 0.1 M HCl + 100 mL of 0.1
M NaOH
C. 100 mL of 0.1 M HCl + 150 mL of 0.1
M NaOH
(cont.)
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
(cont.)
• Which solution is the least toxic?
• Are the final solutions acid, basic, or
neutral?
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
The Big Question
• How can the interactions of acids and
bases be used to determine the
concentration of a particular acidic or
basic solution?
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
You will be able to:
Use the experimental method known as
“titration” to determine the unknown
concentration of an acid or base.
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
Activity
Purpose: This activity will introduce you
to a laboratory procedure used to
determine the concentration of an acid or
a base.
(cont.)
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
(cont.)
HCl solution
Drops of 0.10 M Calculated
NaOH added to concentration
neutralize
of HCl
20 drops HCl
Solution A
20 drops HCl
Solution B
20 drops HCl
Solution C
(cont.)
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
Initial
volume of
HCl
1.0 L
Volume of
0.10 M
NaOH
added
1.0 L
100 mL
200 mL
50 mL
200 mL
Total
moles of
NaOH
0.10
moles
0.020
moles
0.0025
moles
100 mL
Total
Initial HCl
moles of concentrat
HCl
ion
0.10
moles
0.020
moles
0.10 M
0.050 M
73 mL
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
Making Sense
• Describe how you determined the
concentration of the NaOH solution in
Problem 6.
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
Notes
• A titration is a method for determining
the concentration of an acid or base
solution by reacting a known volume of
the solution with a solution of known
concentration. When the moles of H+
are equal to the moles of OH– in the
solution, the reaction has reached the
equivalence point of the titration,
sometimes referred to as the
endpoint.
(cont.)
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
(cont.)
Example:
• If 25.00 mL of 0.50 M nitric acid, HNO3,
solution are required to titrate 62.00
mL of sodium hydroxide, NaOH, what
is the molarity of the NaOH?
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
Check-In
You place 50 drops of HCl in a beaker
along with a drop of phenolphthalein
indicator. After you have added 100
drops of 0.10 M NaOH, the color is a
very faint pink.
• What is the concentration of the HCl
solution?
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
Wrap-Up
• A titration is a procedure that allows
you to calculate the concentration of
an unknown acid or base using a
neutralization reaction.
• During a titration, when the moles of
H+ are equal to the moles of OH– in the
solution, the reaction has reached the
equivalence point of the titration,
sometimes referred to as the endpoint.
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
Toxins Unit – Investigation IV
Lesson 7:
Call Poison Control
ChemCatalyst
Imagine that your little brother spilled a
toxic substance on his skin. You decide
to call Poison Control: 1 (800) 222–1222.
• What are some things that you might
want to know about the substance?
• What kinds of questions do you think
Poison Control will ask you? What
might they tell you to do? Explain your
thinking.
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
The Big Question
• How do solubility and pH contribute to
the toxicity of a substance?
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
You will be able to:
Use the mole concept and balanced
chemical equations to calculate the
mass relationships between products
and reactants and determine the
concentrations or pH of solutions in
which the reactions are a part.
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
Activity
Purpose: The purpose of this worksheet
is to review some of the key ideas in the
Toxins Unit.
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
Making Sense
• No Making Sense exercises.
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
Check-In
• No Check-In exercise.
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X
Wrap-Up
• No Wrap-Up points.
© 2004 Key Curriculum Press.
Unit IV • Investigation IV-X