The only equilibrium calculation

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The only equilibrium calculation Powered By Docstoc
					Indicators
           Strong acids and bases

w The strong acids and bases have no reverse
  reaction.
w They are not an equilibrium reaction.
w HCl + H2O ® H3O+ + Cl-
w No amount of stress will force this reaction the
  other way.
w (no way to make it less acidic, without a
  different reaction)
                    Strong acids
Acid         formula Acid             Formula
Hydrochloric HCl      Sulfuric Acid   H2SO4
acid
Hydrobromic HBr       Nitric Acid     HNO3
acid
Hydriodic acid HI     Perchloric Acid HClO4
              Strong Bases
                      these make a lightning bolt
                      on the periodic table!
Name        Formula   Name          Formula

Sodium      NaOH      Calcium       Ca(OH)2
Hydroxide             Hydroxide
Potassium   KOH       Strontium     Sr(OH)2
Hydroxide             Hydroxide
                      Barium        Ba(OH)2
                      Hydroxide
           Weak acids and bases
w can be forced the other way
w So ammonia…
w NH3 + H2O       NH4++OH-
w Ammonia is a gas with a distinct odor
w Ammonium and hydroxide are both odorless.
w If base is added to the solution you will smell
  ammonia, if hydroxide is removed you
  won’t.
                  Indicators
w Indicators are a substance that change color
  in the presence of (whatever they check for)
w They do this because of Le Châtelier’s
  principle. All you need an equilibrium
  reaction with different colored products and
  reactants.
w The pen used to check for counterfeit money
  is a starch indicator
          How an acid base indicator
                   works
w A generic indicator will follow this reaction, HId 
  is the reactant indicator, and Id- is its product
w HId + H2O      H3O+  + Id- 
w The color differences are important 
w in an acidic solution (high H3O+) you see reactant
wHId + H2O             H3O+  + Id-

w in a basic solution (low H3O+) you see product
                       +       -
w HId + H O         H O   + Id
      2
                     3
                  Acid Base indicators

w Acid base indicators change color at certain
  pH levels
w They don’t have to change at 7 (most don’t)
w Universal indicator solution (phenolphthalein, bromthymol
  blue and methyl red dissolved in ethanol and water) changes color at

  each integral pH value
                  Other pH indicators
w Litmus and
  phenolphthalein
  are indicators
w Red cabbage has
  a pigment that
  changes colors at
  different pH
  values

				
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posted:7/16/2013
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