Chemistry 1011

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Chemistry 1011

• TOPIC
• Acids and Bases
• TEXT REFERENCE
• Masterton and Hurley Chapter 4.2 (Review), 13,
  14.1, 15.1 (page 427), 21.2 (page589)

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13.1 The Bronsted-Lowry Acid-Base Model

• YOU ARE EXPECTED TO BE ABLE TO
• Define an acid as a substance that produces
  hydrogen ions in aqueous solution (Arrhenius)
• Identify common chemical reactions of acids.
• Identify a Bronsted-Lowry acid-base reaction.
• Identify conjugate acid-base pairs.
• Define amphiprotic species.

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The Arrhenius Definition

• An acid is a species that produces hydrogen ions
  in water
• HCl(aq) H(aq) Cl-(aq)
• A base reacts with an acid to produce a salt and
  water only
• HCl(aq) NaOH(aq) NaCl(aq) H2O(l)
• Some bases dissolve in water to give hydroxide
  ions
• NaOH(aq) Na(aq) OH-(aq)
• Some bases are insoluble in water
• 2HCl(aq) CuO(s) CuCl2(aq) H2O(l)

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The Bronsted-Lowry Definition

• An acid is a proton (H ion) donor
• A base is a proton acceptor
• In an acid-base reaction, a proton is transferred
  from the acid to the base
• HB(aq) A-(aq) HA (aq) B-(aq)
• HB and HA are Bronsted-Lowry acids for the
  forward and reverse reactions
• A- and B- are Bronsted-Lowry bases for the
  forward and reverse reactions

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Conjugate Acids and Bases

• B- is the conjugate base of acid HB
• HB is the conjugate acid of base B-
• HB and B- are a conjugate pair
• conjugate
  pair
• conjugate base
  conjugate acid
• HB(aq) A-(aq) HA (aq) B-(aq)
• conjugate acid
  conjugate base
• conjugate
  pair

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Examples of Conjugate Pairs

• Acid
  Base
• HF(aq) H(aq) F-(aq)
• HSO4-(aq) H(aq) SO4-(aq)
• NH4(aq) H(aq) NH3(aq)
• Identify the conjugate pairs in the reaction
• CN-(aq) H2O(l) HCN(aq) OH-(aq)
• cb ca ca
  cb

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Amphiprotic Species

• Some species can act as either Bronsted-Lowry
  acids or bases
• HCO3-(aq) H(aq) CO32-(aq)
• HCO3-(aq) H(aq) H2CO3(aq)
• These species are known as amphiprotic