Acids, Bases, and Salts Ch 15

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Acids, Bases, and SaltsCh 15 16
Introduction to Acids and Bases.asx
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TERM PROJECT

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Properties of Acids Ch 15.1
Properties of acids and bases.asx

• Acid Property 1. The word acid comes from the
  Latin word acere, which means "sour." All acids
  taste sour.
• Acid Property 2. In 1663, Robert Boyle wrote
  that acids would make a blue vegetable dye called
  "litmus" turn red.
• Acid Property 3. Acids destroy the chemical
  properties of bases.

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• Acid Property 4. Acids conduct an electric
  current.
• Acid Property 5. Upon chemically reacting with
  an active metal, acids will evolve hydrogen gas
  (H2).

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Properties of Bases

• Base Property 1. The word "base" has a more
  complex history and its name is not related to
  taste. All bases taste bitter.
• Base Property 2. Bases are substances which will
  restore the original blue color of litmus after
  having been reddened by an acid.
• Base Property 3. Bases destroy the chemical
  properties of acids.

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• Base Property 4. Bases conduct an electric
  current.
• Base Property 5. Bases feel slippery, sometimes
  people say soapy. This is because they dissolve
  the fatty acids and oils from your skin and this
  cuts down on the friction between your fingers as
  you rub them together.

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The Acid Base Theory Ch 15.2

• The three main theories regarding acids and bases
  are
• 1. Arrhenius
• 2. Brønsted-Lowry

3. Lewis
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Svante Arrhenius (1859-1927)
Arrhenius Acids.asx
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Svante Arrhenius

• Swedish chemist (1859-1927) - Nobel prize winner
  in chemistry (1903)
• one of the first chemists to explain the chemical
  theory of the behavior of acids and bases

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1. Arrhenius Definition

• Acids produce hydrogen ions (H1) in aqueous
  solution.
• Bases produce hydroxide ions (OH1-) when
  dissolved in water.
• Limited to aqueous solutions.
• Only one kind of base (hydroxides)
• NH3 (ammonia) could be an Arrhenius base? NH4OH?

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Polyprotic Acids

• Some compounds have more than 1 ionizable
  hydrogen.
• HNO3 nitric acid - monoprotic
• H2SO4 sulfuric acid - diprotic - 2 H
• H3PO4 phosphoric acid - triprotic - 3 H
• Having more than one ionizable hydrogen does not
  mean stronger!

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Johannes Bronsted / Thomas Lowry (1879-1947)
(1874-1936)
Bronsted Acids.asx
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2. Brønsted-Lowry Definitions

• Broader definition than Arrhenius
• Acid is hydrogen-ion donor (H or proton) base
  is hydrogen-ion acceptor.
• Acids and bases always come in pairs.
• HCl is an acid.
• When it dissolves in water, it gives its proton
  to water.
• HCl(g) H2O(l) H3O Cl-
• Water is a base makes hydronium ion.

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Acids and bases come in pairs...
Conjugate acid-bases.asx
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Acids and bases come in pairs...

• A conjugate base is the remainder of the original
  acid, after it donates its hydrogen ion
• A conjugate acid is the particle formed when the
  original base gains a hydrogen ion
• Indicators are weak acids or bases that have a
  different color from their original acid and base

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Acids and bases come in pairs...

• General equation is
• HA(aq) H2O(l) H3O(aq) A-(aq)
• Acid Base Conjugate acid Conjugate
  base
• NH3 H2O NH41 OH1-
• base acid c.a. c.b.
• HCl H2O H3O1 Cl1-
• acid base c.a. c.b.

Amphoteric - acts as acid or base
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Bases and Conjugate Acid
Base Name Conjugate acid Name
CH3OO- Acetate ion CH3COOH Acetic acid
NH3 Ammonia NH4 Ammonium
H2PO4- Dihydrogen phosphate ion H3PO4 Phosphoric acid
HSO4- Hydrogen sulfate ion H2SO4 Sulfuric acid
OH- Hydroxide ion H20 water
NO3- Nitrate ion HNO3 Nitric acid
H2O water H30 Hydronium ion
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Strength
Strong and weak acids.asx

• Strong acids and bases are strong electrolytes
• They fall apart (ionize) completely.
• Weak acids dont completely ionize.
• Strength different from concentration
• Strong-forms many ions when dissolved
• Mg(OH)2 is a strong base- it falls completely
  apart when dissolved.
• But, not much dissolves- not concentrated

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What about bases?

• Strong bases dissociate completely.
• Weak bases only slightly ionize in water

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Strength vs. Concentration

• The words concentrated and dilute tell how much
  of an acid or base is dissolved in solution -
  refers to the number of moles of acid or base in
  a given volume
• The words strong and weak refer to the extent of
  ionization of an acid or base
• Is a concentrated weak acid possible?

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Strong Acids

• HNO3 - nitric acid HCl - hydrochloric
  acidH2SO4- sulfuric acid HClO4 -
  perchloric acid HBr -
  hydrobromic acidHI - hydroiodic
  acid

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Strong Bases

• LiOH - lithium hydroxideNaOH - sodium
  hydroxideKOH - potassium hydroxideRbOH -
  rubidium hydroxideCsOH - cesium
  hydroxideMg(OH)2 - magnesium hydroxideCa(OH)2
  - calcium hydroxideSr(OH)2 - strontium
  hydroxideBa(OH)2 - barium hydroxide

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Self-Ionization of Water
H2O H2O ? H3O OH-
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Kw Ionization Constant for Water
In pure water at 25 ?C
H3O 1 x 10-7 mol/L
OH- 1 x 10-7 mol/L
Kw is a constant at 25 ?C
Kw H3OOH-

• Kw (1 x 10-7)(1 x 10-7) 1 x 10-14

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pH Scale
pH scale in nature.asx

• The pH scale is a measure of hydronium ion
  (H3O) concentration.
• Hydronium ion concentration indicates acidity.
• The higher the H3O, the higher the acidity.

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pH Lab Instructions

• Copy down the chart below on a separate sheet of
  paper. 10 Samples

SAMPLE pH Acid Base Guess Identity



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Calculating pH, pOH
pH scale.asx
pH -log (H3O)
pOH -log (OH-)
Relationship between pH and pOH
pH pOH 14
Finding H3O, OH- from pH, pOH
H3O 10-pH
OH- 10-pOH
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pH and pOH

• See Packet

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Calculator Functions

• See Book page 488

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H, OH-, and pH
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pH Scale
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Measuring pH with wide-range paper
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Narrow-Range pH Paper
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pH Indicators and theirranges
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Acid-Base Reactions

• Neutralization Reaction - a reaction in which an
  acid and a base react in an aqueous solution to
  produce a salt and water
• HCl(aq) NaOH(aq) ? NaCl(aq) H2O(l)
• H2SO4(aq) 2KOH(aq) ? K2SO4(aq) 2 H2O(l)

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Acid-Base Reactions

• Acid Base ? Water Salt
• Properties related to every day
• antacids depend on neutralization
• farmers use it to control soil pH
• formation of cave stalactites
• human body kidney stones from insoluble salts

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Properties of A Salt

• A salt is the combination of an anion (- ion) and
  a cation ( ion).
• Salts are products of the reaction between acids
  and bases.
• Solid salts usually make crystals.
• If a salt dissolves in water solution, it usually
  dissociates into the anions and cations that make
  up the salt.

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Titration

• Titration is the process of adding a known amount
  of solution of known concentration to determine
  the concentration of another solution

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Titration

• The concentration of acid (or base) in solution
  can be determined by performing a neutralization
  reaction
• An indicator is used to show when neutralization
  has occurred
• Often use phenolphthalein- colorless in neutral
  and acid turns pink in base

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Steps - Neutralization reaction

• 1. A measured volume of acid of unknown
  concentration is added to a flask
• 2. Several drops of indicator added
• 3. A base of known concentration is slowly added

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Neutralization

• The solution of known concentration is called the
  standard solution
• added by using a buret
• Continue adding the standard solution until the
  indicator changes color
• called the end point of the titration

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ACID-BASE Equilibria

• Ka Acid- Ionization Constant-
• Kb Base Ionization Constant
• Constant meaning the point at which equilibria is
  reached.
• Weak Acid- Small constant value because of small
  dissociation.
• Strong Acid- Large Constant value because of
  large dissociation.

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ACID-BASE EQULIBRIA CONT

• Steps to Acid- Base Equlibria problem.
• 1. Write out acid/ base equation-
• HA H2O ? H3O A-
• 2. Write out constant expresssion.
• Kb/a H3O A-
• HA-

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ACID BASE STEPS

• Step 3 Remember Concentration of H3O ion and
  the Conjugate base will have the same
  concentration values.
• Ka (X) (X)
• conc
• Step 4. Plug in values and solve.

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Ammonia is a weak base. If the initial
concentration of ammonia is .150M and the
equilibrium concentration of OH- is 1.6 x 10-3,
calculate Kb for ammonia?

• Step 1. Equation- NH3 H2O -gt NH4 OH-
• Step 2 Apply Kb expression- products over
  reactants.
• Step 3plug in and solve
• Answer 1.7 X 10-5

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2.6 mol of a weak acid is added to 1.0 L of
water. At equilibrium the concentration of H3O
is .34M What is the Ka for the acid?

• 5.1 e-2

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What is the pH of 1.0 X 10-3 M NaOH solution?

• 11

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Names and Formulas of Acids

• An acid is a chemical that produces hydrogen ions
  (H1) when dissolved in water
• Thus, general formula HX, where X is a
  monatomic or polyatomic anion
• HCl(g) named hydrogen chloride
• HCl(aq) is named as an acid
• Name focuses on the anion present

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Names and Formulas of Acids

• 1. When anion ends with -ide, the acid starts
  with hydro-, and the stem of the anion has the
  suffix -ic followed by the word acid
• 2. When anion ends with -ite, the anion has the
  suffix -ous, then acid
• 3. When anion ends with -ate, the anion suffix is
  -ic and then acid

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Names and Formulas of Bases

• A base produces hydroxide ions (OH1-) when
  dissolved in water.
• Named the same way as any other ionic compound
• name the cation, followed by anion
• To write the formula write symbols write
  charges then cross (if needed)
• SEE PACKET 18-3 Review

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Gilbert Lewis (1875-1946)
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3. Lewis Acids and Bases

• Gilbert Lewis focused on the donation or
  acceptance of a pair of electrons during a
  reaction
• Lewis Acid - electron pair acceptor
• Lewis Base - electron pair donor
• Most general of all 3 definitions Lewis acids
  dont even need hydrogen!

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• Lewis acid and base