Acids

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Acids Bases
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Learning Outcomes

• Experiment to classify acids and bases using
  their characteristic properties. (Ch 7)
• Include indicators, pH, reactivity with metals

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Learning Outcomes

• Discuss the occurrence of acids and bases in
  biological systems, industrial processes, and
  domestic applications (Ch 8)
• Include safety and health considerations

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Learning Outcomes

• Explain how acids and bases interact to form a
  salt and water in the process of neutralization.
  (Ch 7)

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Learning Outcomes

• Describe the formation and environmental impact
  of various forms of pollution. (Ch 8)
• Examples acid precipitation, ground-level
  ozone, air-borne particulates, smog, ozone
  depletion, respiratory ailments acidified
  lakes.

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7.1 Common Acids and Bases

• Acids
• often occur naturally
• eg) Lactic acid in sore muscles (not enough
  oxygen present during work)
• eg) many fruits including citrus and pineapple

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• Properties
• Taste sour
• Citric Acid C6H8O7
• Feel watery
• Caustic (corrosive)
• They burn

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Svante Arrhenius

• Found that acids are
• ionic compounds and when
• dissolved (aq) they separate
• into their ions.
• He defined acids as substances that
• produce hydrogen ions in solution.

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• HCl ions separate in water to make H and Cl-
• The more H ions present in solution the stronger
  the acid

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• Bases
• Often found naturally in foods or prescription
  drugs.
• Materials which are bases are referred to as
  being basic or alkaline.
• Eg) Quinine is a base found in cinchona bark and
  used to make tonic water and medicine for
  malaria.
• Eg) bases are used to make soap.
• NaOH

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• Properties
• Taste bitter
• Feel slippery
• Caustic (corrosive)
• Eat away
• More dangerous than acids

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• Arrhenius found that bases are ionic compounds
  and when dissolved (aq) they separate into their
  ions. He defined bases as substances that
  produce hydroxide ions in solution.
• NaOH separates in solution to make Na and OH-
• The more OH- ions present in solution the
  stronger the base
• Na(OH) Na OH-

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• NOTE Ammonia NH3 is a base when dissolved in
  water. Why?
• NH3 H2O ? NH4 OH-
• The ammonia atom steals one H from water to form
  OH-
• ammonia atom vs. ammonium ion

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AssignmentP 218 1-4 (20), BLM 7-5BLM 7-6
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7.2 pH A Powerful Scale

• Indicators molecules which change colour with
  changes in the amount of H(aq) ions or OH-(aq)
  ions present.

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• Eg) phenolphthalein
• turns red in base, stays clear in acidic and
  neutral conditions.
• CSI use this to determine presence of blood
• Eg) Litmus paper
• Blue ? Red in Acid
• Red ? Blue in Base

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INDICATORS DO NOT TELL THE STRENGTH OF THE ACID
OR BASE.

Indicator Color in Acid Color in neutral water Color in Base
Red Litmus No change No change Blue
Blue Litmus Red No change No change
Phenolphthalein Turmeric No change Yellow No change No change Red Red
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• Note VERY little indicator is needed in the
  tests. Too much indicator can change the pH of
  the acid or base.
• Example Phenolphthalein is a weak acid.

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• The pH Scale
• pH stands for power of the hydrogen ion
• a scale used to measure the strength of an acid
  or base.
• Is measured with an electronic pH meter OR by
  looking at the colours on Universal indicator
  paper.
• Note neutral solutions have equal numbers of H
  and OH- ions.

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H2O ?? H OH- so pure water is neutral.
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Strongest Acid
Neutral
Strongest Base
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• Each change in 1 pH changes the strength by a
  factor of 10.
• Eg) pH 1 is 103 or 1000 times as strong an acid
  as pH 4.
• Assignment
• -P 225 1-5 (21), BLM 7-7 7-8
• -Fill out chart of important acids
• and bases in notes

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BLM 7-8

1. Base
2. Acid
3. Neither
4. Neither
5. Base
6. Acid

• Acid
• Base
• Neither
• Acid
• Acid
• Acid

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http//www.lab-initio.com/sci_chemistry.html
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7.3 Properties of Acids and Bases

• The strength of an acid is determined by
• 2 factors
• Concentration how much acid is dissolved in
  water.
• Percent Ionization the number of molecules that
  will ionize to release H ions for every 100
  molecules dissolved.

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• Concentration Percent Ionization

H2SO4 ? 2H SO42- None
all Strong
Concentrated Dilute H2CO3 ??2H
CO32- 99mL HCl 1mL HCL 200 1
Weak 1mL H2O 99mL H2O
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Note For Percent Ionization the of H ions in
the acid DOES NOT DETERMINE THE STRENGTH OF THE
ACID

• The strength is only determined by the amount of
  H ions that go into solution
• Not all acids release H ions equally easily.
  (Generally the more polar the bond the stronger
  the acid.)

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• Eg) CH3COOH has 4 H atoms but only 1 ionizes
• CH3COOH ?? CH3COO- H
• Acetic acid
• Copy the charts for common acids and bases on p
  227.
• Why is ammonia considered a base when dissolved
  in water? HINT Guess the products of NH3
  H2O
• NH3 H2O NH4 OH-

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Assignment

• P 230 1-5
• BLM 7-12, 7-13 7-14

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7.4 Neutralization Reactions

• Acids and Bases react with each other to form a
  salt and water.
• Eg) HCl NaOH ? NaCl H2O
• double displacement

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Complete and balance the reactions, name the
salts.

• 2H2O K2(SO4)
• Salt Potassium Sulfate
• 2H2O 1Na2SO4
• Salt Sodium Sulfate
• 2H2O 1Ca(NO3)2
• Salt Calcium Nitrate
• 2H2O MgCO3
• Salt Magnesium Carbonate

• 1H2SO4 2KOH ?
• 1H2SO4 2NaOH ?
• 2HNO3 1Ca(OH)2 ?
• H2CO3 Mg(OH)2 ?

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Making Acids

• Oxides compounds containing one element with
  oxygen.
• Eg) CO, CO2, Al2O3, SO3, NO2
• Non-metal oxides compounds containing a single
  non-metal combined with oxygen.

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• ALL non-metal oxides react with water to form
  acids.
• Eg) CO2 H2O ? H2CO3 carbonic acid (makes
  rain slightly acidic)
• Eg) SO3 H2O ? H2SO4 sulfuric acid

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Assignment

• P 236 1-5
• BLM 7-16, 7-17, 7-19
• Review P 238-239 1-17, 20, 21