ACIDBASE THEORIES

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• CHAPTER 20
• ACID-BASE THEORIES

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• Properties of acids and bases
• Your body needs both acids and bases to function
  properly
• Maintaining proper pH value throughout your body
  system is critical to good health.
• Acids- give food a tartness
• Bases- bitter
• Aqueous solutions of acids and bases are
  electrolytes
• An electrolyte is a solution that conducts
  electricity.
• Both acid and bases can be detected by a color
  change using certain chemical dyes. These dyes
  are called indicators.
• An acid reacts with compounds containing
  hydroxide ions to form water and salt
• A base reacts with an acid to form water and salt.

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• Why do we need to be able to conduct electricity
  in our bodies?
• Send messages to the brain for both voluntary and
  involuntary muscle movements for example.
• Important muscle, heart
• Just to name a few.

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• Acid
• An acid is a compound that produces hydrogen ions
  when dissolved in water
• Therefore the chemical formulas of acids are of
  the general form HX, X representing a monatomic
  or polyatomic anion.
• Rules for assigning names to acids
• 1. when the name ends in ide, the acids name
  begins with hydro, the stem of the anion has the
  suffix-ic and is followed by the word acid.
• Example HCl , Xchloride chloride
• Name hydrochloric acid
• Example 2 H2S X sulfide- hydrosulfuric acid

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• 2. when the anion name ends in ite, the acid
  name has the stem name of ous
• Example H2SO4, sulfurous acid
• 3. anion ending in ate, the stem of the acid is
  given ic
• Example HNO3 nitric acid

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• Identify each property as applying it to an acid,
  base, or both.
• A. bitter taste
• Base
• B. electrolyte
• Both
• C. indicator color change
• Both
• Sour taste
• acid

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• Name each acid or base
• A. HF
• Hydrofluoric acid
• B. HClO3
• Chloric acid
• H2CO3
• Carbonic acid
• Al(OH)3 hint begin with the word aluminum
• Aluminum hydroxide

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• Now write the formula for the following
• Barium hydroxide
• Ba(OH)2
• Hydrobromic acid
• HBr
• Rubidium hydroxide
• RbOH
• Hydroselenic acid (Se is for selenium, row 6A)
• H2Se

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• HYDROGEN IONS FROM WATER
• Collisions between water molecules can occur that
  result with enough energy to transfer a hydrogen
  ion to another water molecule.
• The result is the formation of a hydroxide
  ion(OH-) and hydronium ion(H3O)
• The hydronium ion has been given a few different
  names
• 1.Hydrogen ions
• 2.Hydronium ions
• 3.solvated protons(this is because hydrogen with
  a loss of its only electron is left with just a
• proton.

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• Self-ionization of water is the process of
  converting a molecule of water to either of these
  resulting ions
• In pure water, although there are two different
  ions present, they balance each other out and the
  pH value for pure water is 7.
• Another name given to this situation is Neutral
  solution
• H and OH- are interdependent. Meaning when
  OH- increases H decreases and vise versa.
• Le Chatliers principle, named for the French
  chemist who proposed the concept, states that
  when there is a shift in a equilibrium due to a
  stress brought on by a change in temperature,
  pressure, or concentration, the system will
  change to relieve the stress.

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• If additional ions are introduced to an aqueous
  environment, either H or OH-, there is a shift
  and depending on which is added, the other
  decreases.
• When possible, more water molecules will form to
  neutralize the solution. In a neutral aqueous
  solution, the product of
• H X OH- 1.0 X 10-14 this is called the
• ion-product constant of water or K w
• When the environment can not neutralize with the
  addition of either ion, then a basic (alkaline)
  or acidic situation occurs.

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• To determine OH- content or H content, you can
  manipulate the formula as such
• H K w
• OH-
• Example
• If H in a solution is 1.0 X 10-5 M, is the
  solution acidic, basic, or neutral? pH 5 and it
  is acidic.
• What is the OH- of this solution?
• OH- 1.0 X 10-14 1.0 X 10-9
• 1.0 OH- X 10-5
• The exponent tells you the OH- is 9
• The pH will then be 14 9 5

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• Acid-Base theories
• 1. Arrhenius-defined acids as hydrogen-containing
  compounds that ionize to yield hydrogen ions in
  aqueous solutions and bases as are compounds
  that yield hydroxide ions in aqueous solutions.
• This theory works well to explain HCl converting
  to H and Cl- in aqueous solution as well as Na
  H2O yielding NaOH H2 but is limited for other
  types of bases, such as NH3 that dont contain
  OH ions
• Common acids
• Monoprotic-1 ionizable hydrogen
• Diprotic- 2 ionizable hydrogens
• Triprotic-3 ionizable hydrogens

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• 2. Bronsted-Lowry Acids and Bases is a bit
  broader in its definition. Named after the two
  chemists who independently came up with the
  definition. This theory defines acids as a
  hydrogen-ion donor and bases as a hydrogen-ion
  acceptor.
• Behavior of ammonia as a base is defined by this
  theory but not covered in the Arrhenius theory.
• Ammonia when dissolved in water acts as a base
  because it becomes a hydrogen acceptor from
  water. Water, the hydrogen ion donor is the acid.
• The reverse reaction results in the ammonium ion
  (NH4) as an acid and OH- as the base.

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• When ammonia is dissolved in water, the resulting
  NH4 is referred to as a conjugate acid- by
  definition a conjugate acid is a particle formed
  when a base gains a hydrogen ion.
• A conjugate base is the particle that remains
  after it donates a hydrogen ion.
• NH3 H2O? NH4 OH-
• NH3 is the base, water the acid and NH4 is the
  conjugate acid and OH- the conjugate base.

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• 3. A third theory is more general than either of
  the previously mentioned. A Lewis acid is defined
  as a substance that can accept a pair of
  electrons to form a covalent bond.
• A Lewis base is a substance that can donate a
  pair of electrons to form a covalent bond.
• H -OH? H2O
• H is the Lewis acid and OH- is the Lewis base

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