Acids and Bases Introduction

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Acids and Bases Introduction

• Chem 12
• Chapter 14 Pg 544-559

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Properties of Acids

• Turn blue litmus paper red
• Neutralize the properties of bases
• React with certain metals to produce hydrogen gas
• React with carbonate compounds to produce carbon
  dioxide gas
• Have a sour taste
• Are electrolytes
• Have a pH less than 7

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Properties of Bases

• Turn red litmus paper blue
• Turn the indicator phenolphthalein from colorless
  to red
• Neutralize the properties of acids
• Have a bitter taste
• Are electrolytes
• Are slippery to the touch
• Have a pH greater than 7

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Common Acids

• Sulfuric Acid H2SO4
• Nitric Acid HNO3
• Phosphoric Acid H3PO4
• Hydrochloric Acid HCl
• Acetic Acid CH3COOH
• Carbonic Acid H2CO3

Battery acid
Used to make fertilizers and explosives
Food flavoring
Stomach acid
Vinegar
Carbonated water
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Common Bases
Name Formula Common Name
Sodium hydroxide NaOH lye or caustic
soda Potassium hydroxide KOH lye or caustic
potash Magnesium hydroxide Mg(OH)2 milk of
magnesia Calcium hydroxide Ca(OH) 2 slaked
lime Ammonia water NH3 H2O household ammonia
.
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Definition of Acid

• An operational definition is a definition based
  on observed experimental properties.
• An operational definition of an acid is that it
  is a substance that turns blue litmus paper red
  and has a pH less than 7.

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• An operational definition of a base is that it is
  a substance that turns red litmus paper blue and
  has a pH greater than 7.

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• A conceptual definition attempts to explain why a
  substance behaves the way it does.
• Arrhenius theory (only applies to solutions made
  with water) and Bronsted-Lowery acid base
  definitions are conceptual

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Arrhenius Acid-Base Theory

• An acid is a substance that produces hydrogen
  ions, H (aq), in water. Hydrogen ions always
  combine with at least one water molecule to
  produce hydronium ions, H3O
• HCl(g) H2O(l) lt -- gt H3O (aq) Cl-(aq)
• Arrhenius acid (hydrochloric acid)

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Arrhenius Base

• A base is a substance that produces hydroxide
  ions, OH- (aq), in water.
• NaOH(s) H2O(l) ? Na (aq) OH-(aq)
• Arrhenius base (sodium hydroxide)

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• According to the Arrhenius acid-base theory, the
  hydronium ion explains the chemical properties of
  an acid, and the hydroxide ion explains the
  chemical properties of a base.
• acid-base neutralization the hydronium ion from
  the acid reacts with the hydroxide ion from the
  base to produce water.
• H3O(aq) OH-(aq) ? 2H2O(l)

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Brønsted-Lowry acid-base theory

• An acid is proton (H ion) donor, and a base is a
  proton (H ion) acceptor.
• This is a better definition because it is not
  limited to solutions where water is the solvent.
• Acid (proton donor)

Base (proton acceptor)
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Monoprotic Acids

• Bronsted-Lowry acids can be monoprotic-capable of
  losing one proton, such as
• HCl(aq) H2O(l) ? H3O(aq) Cl-(aq)
• HNO3(aq) H2O(l) ? H3O(aq) NO3-(aq)

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• Bronsted-Lowry acids can also be
  polyprotic-capable of losing (donating) more than
  one proton.
• Polyprotic acids lose their protons in separate
  steps or reactions.

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Diprotic Acids

• Diprotic acids are capable of losing two protons.
  
• H2SO4(aq) H2O(l) ? HSO4-(aq) H3O(aq)
• HSO4-(aq) H2O(l) ? SO42-(aq) H3O(aq)

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Polybasic Bases

• Bronsted-Lowry bases can be monobasic-capable of
  supplying one hydroxide ion such as
• NaOH(s) H2O(l) ? Na(aq) OH-(aq)

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• Polybasic bases can be capable of supplying more
  than one hydroxide ion.
• Dibasic are capable of supplying two hydroxide
  ions.
• Mg(OH)2(s) H2O(l) ? Mg2(aq) 2OH-(aq)

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Conjugate Acid-Base Pairs

• A pair of substances that only differ by one
  proton.
• Conjugate linked together
• H donor
• NH4 CO3-2 lt -- gt NH3 HCO3-
• Acid base conjugate conjugate
• base acid

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• Conjugate acid and base, HA/A-, differ by one
  proton.
• The conjugate acid of a base is the base plus
  the attached proton and the conjugate base of an
  acid
• is the acid minus the proton.

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Conjugate Acid-Base Pairs
Kelter, Carr, Scott, Chemistry A World of
Choices 1999, page 280
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Amphoteric

• Substances that can act like an acid in one
  reaction, and like a base in another type of
  reaction.
• Example baking sodas anion HCO3-
• HCO3- OH- lt -- gt CO3-2 H2O (donates a H, so
  acts like an acid)
• HCO3- H3O lt -- gt H2CO3 H2O (accepts a H, so
  acts like a base)

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Practice

• Finish these questions for homework
• Page 557 1-9