Predicting the Products of Acid-Base Reactions
Using Bronsted Lowry Theory and Solution Chemistry
Chemistry 3202
A Quick Review of LB Theory
- Views acid base reactions as a proton (H+) transfer process.
- Acids lose protons.
- Bases gain protons.
-OR-
- Acids are proton donors.
- Bases are proton acceptors.
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HA
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+
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B
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<====>
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A-
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+
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HB+
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acid
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base
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conjugate base
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conjugate acid
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Review of Solution Processes
When they dissolve...
- Ionic substances dissociate.
- Molecular substances separate.
- Acids substances ionize.
Most acid base reactions occur in aqueous solutions.
Ionic substances dissociate.
- We usually recognize an ionic substances by presence of a metal.
- Common exception - when ammonium ion, (NH4+) is present.
- All are normally solids, formed by oppositely charged ions bonding together in a regularly repeating pattern, forming a crystal lattice.
- Polar water molecules are able to "pull" the ions out of crystal lattice and surround them.
- The ions in solution are individual and separate - dissociated from the lattice and each other.
Ionic substances dissociate.
- Question - What species are present in an aqueous ionic solution?
- Answer - Ions and water molecules.
- Question - What species are found in an aqueous solution of aluminum sulfate, Al2(SO4)3(aq)?
- Answer - There will be Al3+(aq), SO42-(aq), H2O(l)
- All ionic substances are soluble to some degree.
- Most are very soluble.
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Molecular substances separate...
- Molecular substances contain only nonmetal elements.
- They may be solids, liquids, or gases.
- They dissolve due to attractive intermolecular forces with the solvent molecules pulling them into the solvent.
- They exist in solution as the intact, neutral molecule.
- Not all molecular substances are soluble in water.
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Acids ionize ...or do they?
- Arrhenius acids ionize to form hydrogen ions in solution.
- HClO3(aq) ---> H1+(aq) + ClO31-(aq)
- Modernized Arrhenius acids react with water to form hydronium ions.
- H2SO4(aq) + H2O(l) ---> H3O1+(aq) + HSO41-(aq)
- Bronsted Lowry acids lose protons to a base species.
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Predicting the Products of Acid-Base Reactions
A Five Step Method
- List the species actually in solution.
- Identify Bronsted-Lowry Acids (A) and Bases (B)
- Identify the Strongest Acid (SA) and Strongest Base (SB)
- Write the Reaction between the Strongest Acid and Strongest Base
- Determine the Extent of the Reaction
You need:
A Table of Acid-Base Strengths
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