Acids & Bases Notes Page 1
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A c i d s & B a s e s N o t e s P a g e | 1
Unit 12: Acids & Bases (Link to Prentice Hall Text: Chapters 20 & 21)
Name:______
Date Due Assignments Page Number: Problem Numbers
Assignment 1: Naming Acids/Bases 609: 34
Assignment 2: Conjugate Acid/Bases and Definitions 609: 45, 46, 48, 49, 60, 61
Assignment 3: Strong/Weak Acids/Bases 609: 52, 53 640: 49
Assignment 4: Acid/Base Reactions 640: 37, 62
Assignment 5: Normality 640: 43, 44abc, 60
Assignment 6: pH Calculations of Strong Acids/Bases 609: 39, 40, 41, 42
Assignment 7: pH Calculations of Weak Acids/Bases 609: 55, 56, 57, 58, 59, 62
Assignment 8: Titration Calculations 640: 45 A c i d s & B a s e s N o t e s P a g e | 2
Names of Acids & Bases
Rules for Naming Acids
1. Binary Acids (only Hydrogen and one other element present) a. Hydro + root + ic + acid b. Example: HCl =
2. Polyatomic Acids (Hydrogen and polyatomic ion) a. Name is based on polyatomic ion (Table E) b. If ion ends with “ite” change to “ous” + acid c. If ion ends with “ate” change to “ic” + acid
d. Example: H2CO3 =
Rules for Naming Strong Bases
1. Keep the name of the cation and add hydroxide
2. Example: Ca(OH)2 =
Naming Acids & Bases
Name the following acids and bases.
1. HBr______14. Hydroiodic acid______
2. HI______15. Chloric acid______
3. HF______16. Nitric acid______
4. H3PO4______17. Nitrous acid______
5. HClO2______18. Bromic acid______
6. H2SO4______19. Phosphoric acid______
7. HNO3______20. Hydrosulfuric acid______
8. HC2H3O2______21. Sulfuric acid______
9. HNO2______22. Sulfurous acid______
10. KOH______23. Chlorous acid______
11. LiOH______24. Perchloric acid______
12. Ca(OH)2______25. Hydrofluoric acid______
13. Hypochlorous acid______A c i d s & B a s e s N o t e s P a g e | 3
A. Three Theories of Acids and Bases
Arrhenius Theory of Acids and Bases
Acids and bases can be defined in terms of what ions are released when they are dissolved in water.
Acids: Release H + when dissolved in water. + - 1. Example: HCl (g) H (aq) + Cl (aq)
+ + 2. BUT: H does not exist alone in natures so it combines with the lone pair electrons in H2O to make H3O
+ – 3. Therefore: HCl (g) + H2O (l) H3O (aq) + Cl (aq)
+ 4. The properties of an acid therefore depend on the [H3O ]
Categories of Arrhenius Acids 1. Monoprotic –
+ – ex. HCl (g) + H2O (l) H3O (aq) + Cl (aq) 2. Diprotic –
+ 2- ex. H2SO4 + 2H2O (l) 2H3O (aq) + SO4 (aq) 3. Triprotic –
+ 3- ex. H3PO4 + 3H2O (l) 3H3O (aq) + PO4 (aq)
Bases: Release OH - when dissolved in water.
+ - 1. NaOH (s) Na (aq) + OH (aq)
2. KOH (s) K+ (aq) + OH- (aq)
3. Ca(OH)2 (s) ______+ ______A c i d s & B a s e s N o t e s P a g e | 4
Brønsted-Lowry Acids and Bases
Acids and bases can be defined by the ability to donate or accept protons (H + ions). Reactions may not occur in solution phase only.
Acids: Donate protons.
Bases: Accept protons.
Example: HCl (g) + NH3 (g) NH4Cl (s)
Lewis Acids and Bases
Acids and bases can be defined by the ability to donate or accept electron pairs.
Acids: Electron pair receivers.
Bases: Electron pair donors.
Example: NH3 + BF3 NH3BF3
B. Conjugate Acid-Base Pairs
Acids and Bases Come in Pairs
Conjugate Base: Species that exists after a Brønsted-Lowry acid has donated a proton. This species can now accept a proton.
Conjugate Acid: Species that exists after a Brønsted-Lowry base has accepted a proton. This species can now donate a proton.
IMPORTANT: Water is amphoteric, that is, it can act as both a Brønsted-Lowry acid or base depending on what else is in solution. The reaction of water and another acid or base is called hydrolysis. A c i d s & B a s e s N o t e s P a g e | 5
Practice Identifying Conjugate Acid-Base Pairs
Identify the acid(A), base(B), conjugate acid (CA), and conjugate base (CB) in each of the equations.
+ – – – 2– 1. HCl + NH3 → NH4 + Cl 5. HCO3 + OH → H2O + CO3
– – + + 2. OH + HCN → H2O + CN 6. NH4 + H2O → NH3 + H3O
3– – 2– 2– – – 3. PO4 + HNO3 → NO3 + HPO4 7. C2O4 + HC2H3O2 → HC2O4 + C2H3O2
– – 2– – – 4. HCO3 + HCl → H2CO3 + Cl 8. HPO4 + H2O → OH + H2PO4
Fill in the blanks in the table below. When you write the chemical equation, show the reaction for the hydrolysis of the acid (reacting the acid with water) for 1-5 and the reaction for the hydrolysis of the base (reacting the base with water) for 6-10.
Conjugate ACID Conjugate BASE Hydrolysis of Acid
1. H2SO4
2. H3PO4 3. F-
- 4. NO3
- 5. H2PO4 Hydrolysis of Base
2- 6. SO4
2- 7. HPO4
8. H2O
+ 9. NH4
10. H2O A c i d s & B a s e s N o t e s P a g e | 6
C. Identification of Strong/Weak Acids, Bases & Neutral Salts
Strong vs. Weak
Identifying S/W Acids & Bases and Neutral Salts A. Strong Acids
Strong acids =
Seven strong acids: HNO3, H2SO4, HCl, HBr, HI, HClO4, & HClO3
B. Weak Acids Weak acids =
Any formula with an H written in the front of the compound and is not strong, is considered weak.
C. Strong Bases Strong Bases = Hydroxide ion bonded with Group I or I or the bottom half of Group II metals form strong bases.
D. Weak Bases Weak bases =
The conjugate base of a weak acid is a weak base. Weak bases are typically conjugate bases of weak acids (negatively charged) or substances that contain a nitrogen atom with a lone pair (amines). You may see a weak base written as a negative ion alone, or it may be “’disguised” as a salt. A c i d s & B a s e s N o t e s P a g e | 7
E. Neutral Salts Practice Identifying Acidic/Basic/Neutral Substances
Substance S/W A/B or N? Net Ionic Equation for Hydrolysis of Substance
1. H2SO4
2. NaOH
3. HC2H3O2
4. KC2H3O2
5. CH3CH2NH2
2- 6. CO3
7. NaCl
8. KF
9. HCN
10. Ca(OH)2
11. HClO4
12. LiBr
13. NaClO3
14. KNO2
15. NH3
16. H2CO3
17. LiCN
18. CH3NH2
2- 19. SO3
3- 20. PO4
21. (amphoteric) (a) (a) 2- HPO4 (b) (b) A c i d s & B a s e s N o t e s P a g e | 8
D. Chemical Reactions of Acids & Bases
Acid – Metal Reaction (Single Replacement Reaction) 1. Remember: The more active metal gets the partner! Consult Table J. 2. Elements above hydrogen will react with an acid and produce hydrogen gas and a salt.
3. Examples: Ba (s) + 2HCl (aq) H2 (g) + BaCl2 (aq)
4. Practice: Zn + HCl ______+ ______
Neutralization Reaction 1. An acid and a base react together to form water and a salt.
2. Example: HCl (aq) +NaOH (aq) NaCl (aq) + H2O (l)
3. Practice: HNO3 (aq) + KOH (aq) ______+ ______
Acid/Base Chemical Reaction Practice Write the balanced chemical equation for each of the following reactions.
1. _____Ca(OH)2 (aq) + _____HNO3 (aq) ______
2. _____Mg(OH)2 (aq) + _____HCl (aq) ______
3. _____H3PO4 (aq) + ______Ba(OH)2 (aq) ______
4. _____Al (s) + _____ HCN (aq) ______
5. Nitric acid is added to potassium hydroxide. ______
6. Barium hydroxide and hydrobromic acid are mixed. ______
7. Sulfuric acid and calcium hydroxide are mixed. ______
8. Ammonium hydroxide and hydroiodic acid are mixed. ______
9. Nitric acid and magnesium are mixed. ______
10. Aluminum and sulfuric acid are mixed. ______
11. Silver and phosphoric acid are mixed. ______
12. Zinc and acetic acid are mixed. ______A c i d s & B a s e s N o t e s P a g e | 9
E. Acid-Base Indicators
A Reference Table for Indicators Indicators are weak acids or bases that dissociate over a known pH range producing a color change. See Table M in Reference Table for a list of common indicators.
Cabbage Juice Indicator
Purpose: To use a home-made indicator to determine the acidity or basicity of a compound.
Introduction: Red cabbage contains a pigment molecule called flavin (an anthocyanin). This water-soluble pigment is also found in apple skin, plums, cornflowers, and grapes. Very acidic solutions will turn anthocyanin a red color. Neutral solutions result in a purplish color. Basic solutions appear in greenish-yellow. Therefore, it is possible to determine the pH of a solution based on the color it turns the anthocyanin pigments in red cabbage juice.
Red Cabbage Color Key
pH 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Color
Substance Cabbage Juice Color pH Value Table salt (aq)
Vinegar (aq)
Rubbing Alcohol
Lemon juice
Distilled Water
Stomach Acid (aq)
Tums A c i d s & B a s e s N o t e s P a g e | 10
Practice Determining Indicator Colors Using Table M 1. Which indicator is blue in a neutral solution?
2. Name an indicator that is yellow at pH 4.
3. Name an indicator that is yellow at pH 9.
4. What is the pH of a solution that changes methyl orange indicator yellow and litmus red?
5. Which indicator appears colorless in HNO3(aq)?
6. Bromocresol green indicator is added to a beaker containing NaOH(aq). What color change will be observed as HCl is added to the solution in the beaker?
7. Calcium hydroxide is commonly known as agricultural lime and is used to adjust the soil pH. Before the lime was added to a field, the soil pH was 5. After the lime was added, the soil pH changed to 9.
a. A small amount of soil is tested with phenolphthalein, what color would the test be before the agricultural lime is added ?
b. what color would the test be after the agricultural lime is added ? A c i d s & B a s e s N o t e s P a g e | 11
8. Which indicator, when added to a solution, changes color from yellow to blue as the pH of the solution is changed from 5.5 to 8.0?
A) Bromocresol green B) Litmus C) Bromothymol blue D) Methyl orange
9. Which solution will change red litmus to blue?
A) HCl B) NaCl
C) C6H12O6 D) NaOH
10. An acidic solution could have a pH of
A) 12 B) 3 C) 9 D) 7
11. Which 0.1 M solution will turn phenolphthalein pink?
A) HBr
B) CO2 C) LiOH
D) CH3OH A c i d s & B a s e s N o t e s P a g e | 12
F. The pH Scale and pH Calculations with Strong Acids and Bases
+ - Measuring [H3O ] and [OH ] with the pH Scale pH Equations + + -pH pH = - log[H3O ] [H3O ] = 10 pOH = -log[OH-] [OH-] = 10-pOH pH + pOH = 14 + - In acids,[H3O ] _____[OH ] + - In bases, [H3O ]_____[OH ] + - When neutral, [H3O ]_____[OH ] pH scale 0 7 14 acids neutral bases Practice with pH and pOH Calculations
- + Acid or Base? pH pOH [OH ] [H3O ] 1. 3.6
2. 0.01
-9 3. 1 x 10 M Ca(OH)2
4. 2.7 x 10-12M
5. 3.2 x 10-4M HCl 6. 3.2
7. The original pH of a sample is 7.0. Calculate the new pH if the hydronium ion increases by a factor of 1000.
8. The original pH of a sample is 12.0. If the hydroxide ion is decreased by a factor of 100, what is the new pH of the sample? A c i d s & B a s e s N o t e s P a g e | 13
9. The original pH of a sample is 8.00. Calculate the new pH if the hydroxide ion increases by a factor of 10000.
10. The original pH of a sample is 4.0. If the hydronium ion is decreased by a factor of 100, what is the new pH of the sample? A c i d s & B a s e s N o t e s P a g e | 14
G. Normality
Measuring the Extent of Acidity/Basicity with Equivalents Equivalents: The number of moles of H+ or OH- that will be released per mole of acid or base, respectively. For example:
+ + H2SO4 = 2 moles H = 2 equivalents H
1 mole H2SO4
Al(OH)3 =
Measuring the Concentration of Acidity/Basicity with Equivalents Normality Normality, N = Equivalents of H + or OH - Volume (L)
Practice Determining Normality and Equivalents
+ 1. How many equivalents of H are in H3PO4?
- 2. How many equivalents of OH are in Ca(OH)2?
3. What is the normality of 0.3M phosphoric acid?
4. What is the normality of 0.60M H2SO4?
5. What is the normality of 2.5M carbonic acid?
6. What is the normality of 3.2M HCl? A c i d s & B a s e s N o t e s P a g e | 15
H. Titration Calculations
Understanding Titrations and their Corresponding Calculations
Titration is a procedure used in the lab to determine the unknown concentration of a solution (either acidic or basic) using a known titrant. It is based on the stoichiometry of a neutralization reaction.
For example: HCl (aq) + NaOH (aq) H2O (l) + NaCl (aq)
At the end point or equivalence point (signaled by use of an indicator), there are stoichiometrically equal amounts of titrant and unknown.
Titration Equation
NAVA = NBVB
NA and NB are the normalities of the acid and base solutions. VA and VB are the volumes of the acid and base solutions.
Practice with Titration Calculations 1. A 15.00 mL sample of acetic acid is titrated with 34.13 mL of 0.9940 M sodium hydroxide. Determine the molarity of the acetic acid. A c i d s & B a s e s N o t e s P a g e | 16
1. How much of 0.5M H2SO4 is needed to titrate 25.0mL of 0.05M Ca(OH)2?
2. A 20.00 mL sample of diluted hydrofluoric acid requires 13.51mL of a 0.1500M calcium hydroxide to be titrated to the equivalence point. What is the molarity of the acid?
3. A flask contains 41.04mL of potassium hydroxide. The solution is titrated and reaches an equivalence point when 21.65mL of a 0.6515M solution of nitric acid is added. Calculate the molarity of the base solution.
4. What volume of a 0.5200 M solution of sulfuric acid would be needed to titrate 100.00mL of a 0.1225M solution of strontium hydroxide?
5. A 50.0 ml sample of sulfuric acid, H2SO4, is titrated with 35.0 ml of 0.250 M aluminum hydroxide, Al(OH)3. Calculate the molarity of the acid. A c i d s & B a s e s N o t e s P a g e | 17
Calculations of pH & pOH with Weak Acids & Bases Using Ka and Kb
The Acid and Base Dissociation Constant
Acid Dissociation Constant, Ka
+ - + - For the generic reaction: HA (aq) + H2O (l) ↔ H3O (aq) + A (aq) Ka = [H3 O ][A ] [HA]
Base Dissociation Constant, Kb
- - - For the generic reaction: A (aq) + H2O (l) ↔ HA (aq) + OH (aq) Kb = [OH ][HA] [A-]
Practice Determining pH and pOH with Weak Acids and Bases
–4 + - 1. The acid-dissociation constant for hydrofluoric acid, is 7.08 x 10 . Calculate the concentration of H3O , F and HF at equilibrium if the initial concentration of the acid is 0.2 M. What is the pH and pOH of the solution at equilibrium? A c i d s & B a s e s N o t e s P a g e | 18
+ - 2. Determine the [H3O ], [OH ], pH, and pOH for each of the following aqueous weak acids.
-5 a. 1.0M acetic acid (Ka= 1.8 x 10 )
-4 b. 3.0M nitrous acid (Ka= 4.0 x 10 )
-5 c. 6.0M Benzoic acid (monoprotic) (Ka= 6.4 x 10 )
-8 d. 0.01M Hypochlorous acid (Ka= 3.5 x 10 )
3. Write an equation that shows the reaction when the following acids and bases are hydrolyzed. Use the + information below to determine the concentrations of H3O ions.
-4 -5 a. A 2.5 x 10 M solution of NH3 (Kb = 1.8 x 10 )
- -10 b. A 0.5 M solution of C2H3O2 (Kb= 5.6 x 10 ) A c i d s & B a s e s N o t e s P a g e | 19
-10 c. A 0.01 M solution of HCN (Ka= 6.2 x 10 )
-4 d. A 6.5 M solution of HF (Ka= 7.2 x 10 )