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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. - PowerPoint PPT Presentation
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Toxins Unit
Investigation IV: Neutralizing ToxinsLesson 1: HeartburnLesson 2: Watered DownLesson 3: pHooey!Lesson 4: Proton ShuffleLesson 5: Neutral TerritoryLesson 6: Drip DropLesson 7: Call Poison Control
Toxins Unit – Investigation IV
Lesson 1:
Heartburn
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
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?
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
The Big Question
• What are some characteristics of solutions that are acidic, basic, or neutral?
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
You will be able to:
Describe the differences among acidic, basic, and neutral solutions.
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
• Indicators: A set of substances that respond to other substances with vivid color changes.
Notes
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
Activity
Purpose: This activity will introduce you to a special category of solution.
(cont.)
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
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.)
(cont.)
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
Substance Formula Cabbage Juice
Indicator color
Indicator number
table salt (aq) NaCl
vinegar (aq) C2H4O2
rubbing alcohol C3H8O
ammonium hydroxide (aq)
NH4OH
distilled water H2O
stomach acid (aq) HCl
washing soda (aq)
Na2CO3
lemon juice C6H8O7
drain cleaner (aq) NaOH
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
1470
(cont.)
(cont.)
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
Observations when added to CaCO3
water
stomach acid
vinegar
drain cleaner
(cont.)
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
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.
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
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.)
Notes
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
• 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.
(cont.)
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
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.
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
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.
Toxins Unit – Investigation IV
Lesson 2:
Watered Down
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
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?
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
The Big Question
• How does dilution affect the acidity or basicity of a solution?
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
You will be able to:
Explain how dilution affects the concentration and pH of a solution.
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
Activity
Purpose: In this activity you will examine the effect of concentration on acidity and basicity of solutions.
(cont.)
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
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.)
(cont.)
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
Well # Concentration Color pH number
1.0 M HCl
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
Data Table for dilution of 1.0 M HCl
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
Data Table for dilution of 1.0 M NaOH
Well #
Concentration Color pH number
1.0 M NaOH
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
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
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
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
Making Sense
• What does concentration have to do with the acidity or basicity of a solution?
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
1470
More H+ More OH–
pH scale
Notes
(cont.)
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
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.)
(cont.)
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
HA H+ + A–
XOH X+ + OH–
(cont.)
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
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?
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
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.)
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
• 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.
Toxins Unit – Investigation IV
Lesson 3:
pHooey!
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
ChemCatalyst
Examine the following data:
Substance pH
0.10 M HCl 1.0
0.010 M HCl 2.0
0.0010 M HCl 3.0
1.0 M NaOH 14.0
0.10 M NaOH 13.0
0.010 M NaOH 12.0
Water 7.0 (cont.)
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
• What do you think pH really represents?
• How does the concentration of the solutions relate mathematically to the pH of the solutions?
(cont.)
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
The Big Question
• How does pH relate to the concentrations of acidic and basic solutions?
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
You will be able to:
Find the pH of a solution if you know the concentrations of hydrogen or hydroxide ions that it contains.
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
Activity
Purpose: You will explore the relationship between pH, pOH, [H+], and [OH–].
(cont.)
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
Substance Acidic or
Basic?
pH [H+] (in decimal)
[H+] (in scientific
notation)
1 M HCl
Stomach acid (0.1 M HCl) Acidic 0.1 M 1.0 10–1 M
Clear Soda 3 0.001 M
Rain Water Acidic 1.0 10–6 M
Distilled Water 7 0.0000001M
Alcohol Neutral
Salt Water 0.0000001 M
Washing Soda Basic 8 1.0 10–8 M
Ammonia 0.0000000001 M 1.0 10–10 M
Drain Cleaner (0.1 M NaOH)
13
1 M NaOH 1.0 10-14 M
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
Well pH [H+] [OH–] pOH
A 1 1.0 10–1 M 13
B 2 1.0 10–2 M 1.0 10–12 M
12
C 3 1.0 10–3 M
D 4 1.0 10-4 M 1.0 10–10 M
10
E 5 1.0 10–5 M
F 6 1.0 10–6 M
G 7 1.0 10–7 M
H 7 1.0 10–7 M 1.0 10–7 M 7
I 7 1.0 10–7 M 7
HCl
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
Well pH [H+] [OH–] pOH
R 7 1.0 10–7 M 1.0 10–7 M 7
Q 7 1.0 10–7 M 7
P 7 1.0 10–7 M
O 8 1.0 10–8 M
N 9 1.0 10–9 M 1.0 10–5 M 5
M 10 1.0 x10–10 M
L 11 1.0 10–11 M
3
K 12 1.0 10–12
M1.0 10–2 M
J 13 1.0 10–13 M
1.0 10–1 M 1
NaOH
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
Making Sense
• How are pH and pOH related to each other mathematically?
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
This box would show 1,000 H+ ions and 1,000 Cl– ions.
This box would show 100 H+ ions and 100 Cl– ions.
Key: H+ Cl–
pH = 4
Notes
pH = 5 pH = 6 pH = 7
(cont.)
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
pH = –log[H+]
pOH = –log[OH–]
(cont.)
(cont.)
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
Sample Problem:
• What is the pH of a solution with a hydrogen ion concentration of 3.4 10–4 moles/ L?
(cont.)
(cont.)
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
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”.
(cont.)
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
Check-In
• What is the pH of a solution with [OH–] = 1.0 10–12 M?
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
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+]
Toxins Unit – Investigation IV
Lesson 4:
Proton Shuffle
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
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.
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
The Big Question
• Is there a better way to classify acids, bases, and neutral substances?
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
You will be able to:
Explain the behavior of acids and bases on a molecular level.
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
Activity
Purpose: This activity will provide you with information to expand on your definition of acids and bases.
(cont.)
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
(cont.)
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
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.)
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
Acids
(cont.)
(cont.)
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
Bases
(cont.)
(cont.)
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
Neutral Substances(cont.)
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
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.
Notes
(cont.)
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
H2O (l) H+(aq) + OH–
(cont.)
(cont.)
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
NH3 (aq) + H2O (l) NH4+ (aq) + OH– (aq)
(base) (acid)
HNO3 H+ + NO3–
HNO3 + H2O H3O+ + NO3–
(acid) (base)
pH = –log[H3O+]
(cont.)
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
Check-In
• Do you predict a solution of CH4 to be acidic, basic or neutral? Explain.
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
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.
Toxins Unit – Investigation IV
Lesson 5:
Neutral Territory
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
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?
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
The Big Question
• How do acids and bases interact with each other?
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
You will be able to:
Write balanced chemical equations describing the interactions between acids and bases.
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
Activity
Purpose: In this activity, you will examine the products of reactions between acids and bases.
(cont.)
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
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
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
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
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
• A neutralization reaction is a reaction in which an acid and a base react in aqueous solution to produce a salt and water.
Notes
(cont.)
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
HA + MOH MA + H2O
(cont.)
(cont.)
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
2HCl (aq) + Mg(OH)2
MgCl2 (aq) + 2 H2O (l)
(cont.)
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
Check-In
• Sulfuric acid, H2SO4, reacts with magnesium hydroxide, Mg(OH)2. Write a balanced equation for the reaction that occurs.
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
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.
Toxins Unit – Investigation IV
Lesson 6:
Drip Drop
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
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.)
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
• Which solution is the least toxic?
• Are the final solutions acid, basic, or neutral?
(cont.)
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
The Big Question
• How can the interactions of acids and bases be used to determine the concentration of a particular acidic or basic solution?
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
You will be able to:
Use the experimental method known as “titration” to determine the unknown concentration of an acid or base.
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
Activity
Purpose: This activity will introduce you to a laboratory procedure used to determine the concentration of an acid or a base.
(cont.)
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
HCl solution Drops of 0.10 M NaOH added to neutralize
Calculated concentratio
n of HCl
20 drops HCl Solution A
20 drops HCl Solution B
20 drops HCl Solution C
(cont.)
(cont.)
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
Initial volume of HCl
Volume of 0.10 M
NaOH added
Total moles of NaOH
Total moles of
HCl
Initial HCl concentra
tion
1.0 L 1.0 L 0.10 moles
0.10 moles
0.10 M
100 mL 200 mL 0.020 moles
0.020 moles
50 mL 200 mL
0.0025 moles
0.050 M
100 mL 73 mL
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
Making Sense
• Describe how you determined the concentration of the NaOH solution in Problem 6.
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
• 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.
Notes
(cont.)
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
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?
(cont.)
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
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?
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
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.
Toxins Unit – Investigation IV
Lesson 7:
Call Poison Control
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
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.
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
The Big Question
• How do solubility and pH contribute to the toxicity of a substance?
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
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.
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
Activity
Purpose: The purpose of this worksheet is to review some of the key ideas in the Toxins Unit.
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
Making Sense
• No Making Sense exercises.
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
Check-In
• No Check-In exercise.
Unit IV • Investigation IV-X
© 2004 Key Curriculum Press.
Wrap-Up
• No Wrap-Up points.