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Physical Science chp. 9 Acid and Base
Physical Science Chapter 9: Families  of  Chemical  Compounds

9-1           Acids  and  Bases

All acids and bases have certain physical and chemical properties when dissolved in water.


"    sour taste
"    indicators change colors (litmus paper turns red)
"    react with metals to form hydrogen gas and metal compounds
"    react with bases to form salt and water
"    contain hydrogen
"    corrosive

Acids contain hydrogen and in water an acid will produce hydrogen ions (H+)

Acids are proton donors

H+ in water forms the  hydronium ion:  H3O+

Common acids: sulfuric           H2SO4   (Strong)
                         nitric               HNO3   (Strong)
                         hydrochloric   HCl    (Strong)
                  citric acid (in orange juice)


"    bitter taste
"    slippery
"    litmus paper turns blue
"    dissolve fats and oils
"    react with acids to produce salts and water

Bases contain the hydroxide ion:   OH-

The (OH- ) hydroxide ion can combine with (H+) hydrogen ions so bases are defined as proton acceptors.

Common Bases:
          potassium hydroxide    KOH  (Strong)
                 sodium hydroxide        NaOH  (Strong)
                 calcium hydroxide      Ca(OH)2   
          *drain cleaners and antacids

Acids and Bases and Electrical Conductivity:  They are conductive due to the presence of ions in the solution. (Acid has H+ ions, bases have OH- ions.)

   Strong acid/bases are good electrolytes.
   Weak acid/bases are poor electrolytes.

Acids and Bases Indicators:
   Litmus paper, pH meter, pH paper, pehnolphthalein

9-2          Acids and Bases in Solution: Salts

The pH scale is used to measure the acidity of a solution.  The strength of an acid or base depends on how completely a compound is pulled apart to form ions when dissolved in water.

The pH of a solution is a measure of the hydronium ion (H3O+) concentration.

pH goes from 0 to 14

                  pH 7 is neutral   (Water)

      <7 is an acid                   >7 is a base
    (1 is most acidic)            (14 is most basic)

Acid plus Base is a "neutralization" chemical reaction.(Always produce salt and water)

The products of an acid and a base are salt and water.  Many salts formed as a result of a neutralization reaction are not soluble in water so they crystallize out of solution.  They are called precipitates.