chapter 16 acidsandbases.ppt

Chapter 16 Acids and Bases
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Arrhenius theory of acids and bases
The Arrhenius concept: acids dissociate in water (aqueous solution) to produce hydrogen ions H+, and bases dissociate in water to give hydroxide ions, OH-.
Arrhenius acid: HA (aq)  H+ (aq) + A- (aq)
Arrhenius base: MOH (aq)  M+ (aq) + OH- (aq)
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Neutralization reactions
Arrhenius acids and bases react with each other to form water and aqueous salts in neutralization reactions.
H+ (aq) + A- (aq) + M+ (aq) + OH- (aq)  H2O (l) + M+ (aq) + A- (aq)
ionic equation is
H+ (aq) + OH- (aq)  H2O (l)
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Aqueous salts
The aqueous salt in the es from the spectator ions in the reaction. These ions are present to balance the proton positive charge or the hydroxide ion negative charge in the acid or base.
If we evaporate all the water, we are left with an ionic solid called a salt . NaCl
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Arrhenius theory of acids and bases
Many substances that do not contain OH- act like bases!
The key to the Arrhenius description is that we need water to act as a solvent to promote the dissociation of the acid or base.
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Brønsted-Lowry theory of acids and bases
Many substances (like NH3) that do not contain OH- act like bases in water!
The Brønsted-Lowry Theory: an acid is any substance that donates protons (H+) while a base is any substance that can accept protons.
This means that Brønsted-Lowry acid-base reactions are proton transfer reactions.
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Proton transfer reactions
Pairs pounds are related to each other through Brønsted-Lowry acid-base reactions. These are conjugate acid-base pairs.
Generally, an acid HA has a conjugate base A- (a proton has transferred away from the acid). Conversely, a base B has a conjugate acid BH+ (a proton has transferred toward the base).
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Water as an acid in BL reactions
When a Brønsted-Lowry base is placed in water, it reacts with the water (which acts as a Brønsted-Lowry acid) and establishes an acid-base equilibrium.
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BL base strength
The strength of a