Acids and Bases

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Acids and Bases
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What are Acids?

• Acids are common
• Some are dangerous and can burn your skin
• Some are safe to eat and drink
• Stomach acid helps digest food

explosion
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Acids

• Produce H (as H3O) ions in water
• Produce a negative ion (-) too
• Taste sour
• Corrode metals
• React with bases to form salts and water

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Acids

• Definition
• A group of compounds which behave similarly
• All have low pH
• Turn Litmus paper RED
• All donate H ions in aqueous solution
• Examples
• Hydrochloric HCl
• Sulfuric H2SO4
• Nitric HNO3
• Ethanoic CH3COOH

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What are Bases (Alkalis)?

• In our home we often use bases to clean things.
  Eg Bleach and toothpaste
• Some things are not acids or bases, we say that
  they are neutral. Eg Water

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Bases

• Definition
• A family of compounds that behave similarly
• Have a high pH
• Turn litmus BLUE
• All donate OH-
• Examples
• Ammonia NH3
• Sodium Hydroxide NaOH

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Bases

• Produce OH- ions in water
• Taste bitter, chalky
• Are electrolytes
• Feel soapy, slippery
• React with acids to form salts and water

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Measuring acid strength?

• To decide if something is an acid or a base we
  can use an indicator.
• Litmus and Universal Indicator are examples of
  indicators.
• They change colour depending on if they are in an
  acid or a base.

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Working with Indicators

• Red litmus turns BLUE in the presence of Bases
• Blue litmus turns RED in the presence of acid
• Acids and bases react together in a
  NEUTRALISATION reaction

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Learning Check AB1

• Describe the solution in each of the following
  as 1) acid 2) base or 3)neutral.
• A. ___soda
• B. ___soap
• C. ___coffee
• D. ___ wine
• E. ___ water
• F. ___ grapefruit

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Solution AB1

• Describe each solution as
• 1) acid 2) base or 3) neutral.
• A. _1_ soda
• B. _2_ soap
• C. _1_ coffee
• D. _1_ wine
• E. _3_ water
• F. _1_ grapefruit

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Learning Check AB2

• Identify each as characteristic of an A) acid
  or B) base
• ____ 1. Sour taste
• ____ 2. Produces OH- in aqueous solutions
• ____ 3. Chalky taste
• ____ 4. Is an electrolyte
• ____ 5. Produces H in aqueous solutions

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Solution AB2

• Identify each as a characteristic of an A) acid
  or B) base
• _A_ 1. Sour taste
• _B_ 2. Produces OH- in aqueous solutions
• _B_ 3. Chalky taste
• A, B 4. Is an electrolyte
• _A_ 5. Produces H in aqueous solutions

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Some Common Acids

• HCl hydrochloric acid
• HNO3 nitric acid
• H3PO4 phosphoric acid
• H2SO4 sulfuric acid
• CH3COOH acetic acid

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Some Common Bases

• NaOH sodium hydroxide
• KOH potassium hydroxide
• Ba(OH)2 ________________________
• Mg(OH)2 ________________________
  Al(OH)3 aluminum hydroxide

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Learning Check AB4

• Match the formulas with the names
• A. ___ HNO2 1) hydrochloric acid
• B. ___ Ca(OH)2 2) sulfuric acid
• C. ___ H2SO4 3) sodium hydroxide
• D. ___ HCl 4) nitrous acid
• E. ___ NaOH 5) calcium hydroxide

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Solution AB4

• Match the formulas with the names
• A. _4__ HNO2 1) hydrochloric acid
• B. _5__ Ca(OH)2 2) sulfuric acid
• C. _2__ H2SO4 3) sodium hydroxide
• D. _1__ HCl 4) nitrous acid
• E. _3__ NaOH 5) calcium hydroxide

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Learning Check AB5

• Acid, Base Name
• or Salt
• CaCl2 ______ _________________
• KOH ______ _________________
• Ba(OH)2 ______ _________________
• HBr ______ _________________
• H2SO4 ______ __________________

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Solution AB5
Acid, Base Name or Salt CaCl2
salt calcium chloride KOH base potassiuim
hydroxide Ba(OH)2 base barium
hydroxide HBr acid hydrobromic
acid H2SO4 acid sulfuric acid

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Acids

• A dilute acid has lots of water and a small
  amount of acid
• A concentrated acid has lots of acid and not much
  water so must be handled carefully
• A strong acid releases lots of H
• A weak acid releases fewer H

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Strong and Weak Acids and Bases

• Strong acids
• HCl, HNO3 , H2SO4
• Most other acids are weak.
• Strong bases
• NaOH, KOH, and Ca(OH)2
• Most other bases are weak.

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Antacids

• Used to neutralize stomach acid (HCl)
• Many contain one or more weak bases
• Alka-Seltzer NaHCO3, citric acid, and aspirin
• Di-gel CaCO3 and Mg(OH)2
• Gelusil Al(OH)3 and Mg(OH)2
• Maalox Al(OH)3 and Mg(OH)2
• Mylanta Al(OH)3 and Mg(OH)2

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More Antacids

• Milk of Magnesia Mg(OH)2
• Rolaids AlNa(OH)2CO3
• aluminum sodium dihydroxy carbonate
• Tums CaCO3
• Tempo CaCO3, Al(OH)3, Mg(OH)2

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Dilutions

• Add water
• Volume increases.
• New concentration is less than initial

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pH

• Indicates the acidity H3O of the solution
• pH - log H3O
• From the French pouvoir hydrogene
• (hydrogen power or power of
• hydrogen)

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pH Range

• 0 1 2 3 4 5 6 7 8 9 10 11 12
  13 14
• Neutral
• HgtOH- H OH-
  OH-gtH

Acidic
Basic
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pH of Some Common Acids

• gastric juice 1.0
• lemon juice 2.3
• vinegar 2.8
• orange juice 3.5
• coffee 5.0
• milk 6.6

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pH of Some Common Bases

• blood 7.4
• tears 7.4
• seawater 8.4
• milk of magnesia 10.6
• household ammonia 11.0

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Acid Rain

• Consider
• Causes
• natural
• human
• Effects
• buildings
• flora
• fauna
• health
• Chemical equations
• Prevention/Solution

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Acid Rain

• Unpolluted rain has a pH of 5.6
• Rain with a pH below 5.6 is acid rain
• CO2 in the air forms carbonic acid
• CO2 H2O H2CO3
• Adds to H of rain
• H2CO3 H (aq) HCO3-(aq)
• Formation of acid rain
• 1. Emission of sulfur and nitrogen oxides from
  the burning of fuels expecially coal with high S
  content, power stations, oil refineries,
  vehicles as well as bacterial decomposition, and
  lighting hitting N2
• SO2 26 million tons in 1980
• NO and NO2 22 million tons in 1980
• Mt. St Helens (1980) 400,000 tons SO2
• 2. Reactions in the atmosphere form SO3
• 2SO2 O2 ?? 2 SO3
• 3. Reactions with atmosphere water form acids

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Sources of Acid Rain

• Power stations
• Oil refineries
• Coal with high S content
• Car and truck emissions
• Bacterial decomposition, and lighting hitting N2

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• SO2 26 million tons in 1980
• NO and NO2 22 million tons in 1980
• Mt. St Helens (1980) 400,000 tons SO2
• Reactions with oxygen in air form SO3
• 2SO2 O2 2 SO3
• Reactions with water in air form acids
• SO3 H2O H2SO4 sulfuric acid
• NO H2O HNO2 nitrous acid
• HNO2 H2O HNO3 nitric acid

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Effects of Acid Rain

• Leaches Al from soil, which kills fish
• Fish kills in spring from runoff due to
  accumulation of large amounts of acid in snow
• Dissolves waxy coatings that protect leaves from
  bacteria
• Corrodes metals, textiles, paper and leather