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ICE Charts
Calculating Ka
Calculating Kb from Ka and Ka from Kb
Mission 1: Lewis Acids & Bases
Mission Objectives. You should be able to...
1. Describe a Lewis acid and a Lewis base.
2. Explain how a coordinate bond is formed.
3. Differentiate between nucleophiles and electrophiles and provide examples.
Lewis' definition of acids and bases focuses on the behavior of electrons. Acids accept electron pairs and bases donate electron pairs. Lewis's theory is broader than Bronsted-Lowry's, which allows for a wider variety of substances to be included. Ammonia (NH3) and OH- act as Lewis bases. H+ is a Lewis acid. On page 396, you'll see the example of boron trifluoride sharing electron pairs with ammonia. Ammonia donates a lone pair of electrons to BF3 to form a coordinate bond. The arrow represents a coordinate bond in which one atom contributes both electrons involved in forming the covalent bond.
Ligands are ions/moleules attached to metal atoms by coordinate bonding OR a molecule that binds to another (larger) molecule. Transition metals have partially occupied d-subshells so they can form complex ions with ligands that have lone pairs. The metal atom/ion acts as the Lewis acid and the ligand acts as a Lewis base. Check page 397.
Nucleophiles are electron-rich with at leasst one lone pair. They act as Lewis bases. Electrophiles are electron-deficient that can accept a lone pair from a nucleophile. They act as Lewis acids.
ICE Charts
Calculating Ka
Calculating Kb from Ka and Ka from Kb
Mission 1: Lewis Acids & Bases
Mission Objectives. You should be able to...
1. Describe a Lewis acid and a Lewis base.
2. Explain how a coordinate bond is formed.
3. Differentiate between nucleophiles and electrophiles and provide examples.
Lewis' definition of acids and bases focuses on the behavior of electrons. Acids accept electron pairs and bases donate electron pairs. Lewis's theory is broader than Bronsted-Lowry's, which allows for a wider variety of substances to be included. Ammonia (NH3) and OH- act as Lewis bases. H+ is a Lewis acid. On page 396, you'll see the example of boron trifluoride sharing electron pairs with ammonia. Ammonia donates a lone pair of electrons to BF3 to form a coordinate bond. The arrow represents a coordinate bond in which one atom contributes both electrons involved in forming the covalent bond.
Ligands are ions/moleules attached to metal atoms by coordinate bonding OR a molecule that binds to another (larger) molecule. Transition metals have partially occupied d-subshells so they can form complex ions with ligands that have lone pairs. The metal atom/ion acts as the Lewis acid and the ligand acts as a Lewis base. Check page 397.
Nucleophiles are electron-rich with at leasst one lone pair. They act as Lewis bases. Electrophiles are electron-deficient that can accept a lone pair from a nucleophile. They act as Lewis acids.
Mission 2: Calculations
Mission Objectives. You should be able to...
1. Solve problem involving [H+], [OH-] (both aq), pH, pOH, Ka, pKa, Kb, and pKb.
2. Discuss the relative strengths of acids and bases using values of Ka, Kb, pKa and pKb.
Strong acids/bases ionize completely. Weak acids/bases ionize partially. What this means is that strong acids and bases break up into their component ions completely. Weak acids and bases do not. When writing equations demonstrating this, strong acids and bases are written with a solid arrow, whereas weak acids and bases are written using the equilibrium arrows.
We can determine the concentration [ ] of the disassociated weak acid using the relationship between [ ] of reactants and products. Look at the example problems on p. 399, 401 & 402.
Khan Academy has a lovely article relating Ka & Kb, and how they relate to pH. Ka is the acid disassociation constant and Kb is the base disassociation constant. They are related to the ion product constant: Kw = Ka * Kb. Basically, pKa is the -log (Ka) and pKb is the -log (Kb). These values predict whether a species will donate or accept protons at a specific pH value. pKa + pKb = 14
These values also describe the degree of ionization of an acid or base and are true indicators of acid base strength because adding water does not change the equilibrium constant.
Small pKa --> large Ka (strong acid). Small pKb --> large Kb (strong base). Below are the relationships.
Mission Objectives. You should be able to...
1. Solve problem involving [H+], [OH-] (both aq), pH, pOH, Ka, pKa, Kb, and pKb.
2. Discuss the relative strengths of acids and bases using values of Ka, Kb, pKa and pKb.
Strong acids/bases ionize completely. Weak acids/bases ionize partially. What this means is that strong acids and bases break up into their component ions completely. Weak acids and bases do not. When writing equations demonstrating this, strong acids and bases are written with a solid arrow, whereas weak acids and bases are written using the equilibrium arrows.
We can determine the concentration [ ] of the disassociated weak acid using the relationship between [ ] of reactants and products. Look at the example problems on p. 399, 401 & 402.
Khan Academy has a lovely article relating Ka & Kb, and how they relate to pH. Ka is the acid disassociation constant and Kb is the base disassociation constant. They are related to the ion product constant: Kw = Ka * Kb. Basically, pKa is the -log (Ka) and pKb is the -log (Kb). These values predict whether a species will donate or accept protons at a specific pH value. pKa + pKb = 14
These values also describe the degree of ionization of an acid or base and are true indicators of acid base strength because adding water does not change the equilibrium constant.
Small pKa --> large Ka (strong acid). Small pKb --> large Kb (strong base). Below are the relationships.
Mission 3: pH Curves
Mission Objectives: You should be able to...
1. Sketch the general shape of graphs of pH against volume for titrations involving strong and weak acid and bases with an explanation of their features.
2. Select an appropriate indicator for a titration given the equivalence point of the titration and the end point of the indicator.
3. Understand the preparation of buffer solutions.
4. Predict the relative pH of aqueous salt solutions formed by different combinations of acids and bases.
A buffer is a solution that resists a change in pH. It can be a weak acid and its conjugate base OR a weak base and its conjugate acid. You will learn about the four kinds of pH curves: (1) titration of a strong acid and a strong base, (2) titration of a weak acid and a strong base, (3) titration of a weak base and a strong acid, and (4) titration of a weak base and a weak acid.
Indicators are typically a weak acid or a weak base that displays a different color in acidic or alkaline environments. Many indicators act as weak acids. An indicator can also be a weak base.
Selection of an indicator.
Mission Objectives: You should be able to...
1. Sketch the general shape of graphs of pH against volume for titrations involving strong and weak acid and bases with an explanation of their features.
2. Select an appropriate indicator for a titration given the equivalence point of the titration and the end point of the indicator.
3. Understand the preparation of buffer solutions.
4. Predict the relative pH of aqueous salt solutions formed by different combinations of acids and bases.
A buffer is a solution that resists a change in pH. It can be a weak acid and its conjugate base OR a weak base and its conjugate acid. You will learn about the four kinds of pH curves: (1) titration of a strong acid and a strong base, (2) titration of a weak acid and a strong base, (3) titration of a weak base and a strong acid, and (4) titration of a weak base and a weak acid.
Indicators are typically a weak acid or a weak base that displays a different color in acidic or alkaline environments. Many indicators act as weak acids. An indicator can also be a weak base.
Selection of an indicator.
In the below video, Sal Khan reviews titration curves. You can watch the whole video if you like, but I would focus on the first 5-6 minutes, when he reviews the four titration curves.