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What is the pH for this

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					Acids, Bases & pH
                  WATER
Before understanding Acids and Bases, you must
    understand water.
l It is a polar covalent molecule. Like a
    magnet.




              -     +
                           -    +
                  WATER
l   It is a polar covalent molecule. WHY???
Oxygen pulls on the electrons more than Hydrogen does.




                     -   +     -   +
                WATER
Because water is POLAR (negative side and
   positive side), what types of compounds will
   it DISSOLVE easily?
Covalent or Ionic?




                  -   +    -   +
  Ionic Compounds: Acids



                               Or written as HCl à H3O+ + Cl-


Ionic compounds that break apart (dissolve) in water to
     form a hydronium ion, H3O+ (hydrogen ion, H+).
                            3
                              +



The more H+ ions released in water = STRONGER ACID
          +
                Acids



                           Or written as HCl à H3O+ + Cl-


When HCl is put in water, a Hydronium ion, H3O+
                                            3
                                              +

          (hydrogen ion, H+) is formed.
          Acids, Bases and pH
           Why do we need to know?




The pH of a substance determines its physical and
              chemical properties .
              Acids
     Characteristics of Acids
     • Taste Sour
     • React Strongly with Metals and
       Carbonates (in soil and rocks)
     • Can burn your skin
     • Conduct electricity in water
     • Turn indicator red
Examples of Acids
• Vinegar
• Citrus fruits
• Stomach Acid (HCl)
Ionic Compounds: Bases


                              NaOH à Na+ + OH-


Ionic compounds that break apart (dissolve) in water
   to form a negatively charged hydroxide ion (OH-).

More OH-- ions released in water = STRONGER BASE
          Acids, Bases and pH
           Why do we need to know?




The pH of a substance determines its physical and
              chemical properties .
          Bases
       Characteristics of Bases
       • Taste bitter
       • Feel Slippery
       • Can burn your Skin
       • Turn indicator blue
       • Conduct electricity in water

Examples of Bases
•  Lye (Sodium Hydroxide)
•  Ammonia
•  Bleach
                          pH
              What does it mean?

    pH – potential of Hydrogen – the
          ability to release H+

The more H+ released in water, the HIGHER
                  the pH.
   Which one below releases more H+?
        • HBr à H3O+ + Br-
          HBr
          or written as
          or written as   HBr à H+ + Br--
                          HBr   H+ + Br
         2. KOH à K+ + OH-
         2. KOH
                   pH
Which has a greater ability to release H+ in
     water? Which has HIGHER pH?

          HBr à H+ + Br-
          HBr
YES! And therefore this shows a higher pH
          (potential of Hydrogen)

         KOH à K+ + OH-
         KOH
NO! And therefore this shows a lower pH
         (potential of Hydrogen)
          pH
COMPARE: WHAT ARE THEIR pH
        VALUES?????

     HBr à H+ + Br-
     HBr
         About 1 to 2

     KOH à K+ + OH-
     KOH
       About 13 to 14
                      pH
pH – potential of Hydrogen – the ability to release H+
     potential    Hydrogen



WHAT ABOUT NEUTRAL WATER?

                H2O ßà H+ + OH--
                 2
                        +



            What is the pH for this?
                      pH
pH – potential of Hydrogen – the ability to release H+


NEUTRAL WATER: H2O ßà H+ + OH--
                2
                       +


                 NEUTRAL = pH 7

           HOW DOES THIS HAPPEN?
                   pH
             H2O ßà H3O+ + OH--
              2      3
                       +



                     pH 7
Dissociation – the breaking apart of water into
               ions. H3O+ = OH--
                      3
                         +
               The pH Scale
Tells the concentration of (how many) hydrogen (H+)
                                                 +

                  ions in solution.
        Hydrogen Ion Concentration in Moles/Liter at 25° C
                        pH           H+ conc.
                         0              1.0
                         1              0.1
                         2             0.01
                         3             0.001
                         4            0.0001
                         5            0.00001
                         6           0.000001
                         7           0.0000001
                         8          0.00000001
                         9          0.000000001
                        10         0.0000000001
                        11         0.00000000001
                        12        0.000000000001
                        13        0.0000000000001
                        14       0.00000000000001
           The pH Scale
Tells the concentration of (or how many) hydrogen (H+)
ions in a water solution.




    Each move up the scale is a jump of 10 TIMES.
HOW MANY TIMES?
l   How many times stronger is pH 3, than pH 4?
l   pH3 is 10 times stronger than pH4
l   Or another way, 1 jump up the scale equals 10 times more
    H+ ions!
l   How many times stronger is pH 5, than pH 8?
l   3 jumps up the scale?
l   10 x 10 x 10
l   1,000 times more H+ ions! 1,000 times stronger!
l   How about pH 1 than pH 7?
l   6 jumps
l   10 x 10 x 10 x 10 x 10 x 10
l   1,000,000 times! 1,000,000 times MORE H+ ions!
             The pH Scale
l   The 0 – 14 pH scale was created to show
    amount of H+ ions in a water solution.

l   pH of a neutral solution = 7
        H+ concentration = OH- concentration


l   Acidic pH values: 0 – 6, MAXIMUM = 0
l   Basic pH values: 8 – 14, MAXIMUM = 14
             Indicator
Indicator – changes color as the pH changes, and
        thus tells us the pH of a solution.
               NEUTRALIZATION
l   What happens when an ACID is added to a
    BASE ????
l   They react to form a salt and water
       Hydrochloric Acid + Sodium Hydroxide à Water + Table Salt

             HCl + NaOH à H2O + NaCl
Acids and Bases and Neutralization

 l   One of the most important aspects of a living
     system is the amount of acidity or alkalinity
                 NEUTRALIZATION:
                 NEUTRALIZATION
               Why do we need to know?


l   Control of pH is very
    important
l   Control is accomplished with
    buffers
                         pH
              Why do we need to know?




l   Buffers neutralize
    small amounts of
    either an acid or
    base.
                              pH
                 Why do we need to know?




Alkalinity – the ability of a stream to neutralize acids.
STOP HERE

				
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posted:10/18/2013
language:English
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