Material   :one tea bag                         a little bit of 3% peroxide
                saucepan                             about 100 ml of vinegar
                two glasses                          steel wool
                one cotton swab

Experiment :  Prepare a cup of strong black tea.
                    To prepare a solution containing iron III, boil under vent over the stove about 100 ml
                    of vinegar to which a pad of steel wool has been added. Allow the solution to
                    simmer for 5 to 10  minutes, and then carefully  pour the top of the solution in
                    a glass in such a way that you do not collect any steelwool.
                    When this last solution is cool ( room temperature) add a little bit of hydrogen
                    peroxide. The color of the solution should now be a dark brownish red,
                    indicating the presence of iron III.
                    To produce ferric tannate add some of your tannic solution to an equal amount
                    of your solution of iron III. The solution should turn black as a result of ferric
                    (iron III tannate ) being produced.

                    FERRIC TANNATE MAY STAIN, SO be careful to avoid contact with your
                    clothing; it is the major ingredient of many black inks.

                    Do not throw away this black ink until you have completed the report: you will need
                    some as the last evidence!

PLEASE PRINT THIS REPORT AND COMPLETE.   Name:____________________

   1. Reactions:   a)                            2 H+     +    Fe     =    Fe 2+     +       H2

                         b)       2  H+    +  2Fe 2+  +  H2O2     =    2Fe 3+     +   2 H2O

                         c)               Fe 3+   +  tannic acid         =    ferric tannate
 

            Fill in the blanks

                           Vinegar, an acid provides ___________to the steelwool and

                           transforms iron element in iron +2.  Iron is therefore ___________

                          ( oxidized / reduced) and called the _____________(oxidizing/reducing)agent.

                          On the other hand H+ is ___________and called the _____________agent.

                          In a second step, iron II is _____________in iron III while reacting with

                         hydrogen peroxide. Hydrogen peroxide is a strong ___________agent. It
 
                        is also a powerful bleach!!

                         Reactions a) and b) are _____________reactions because the oxidation

                        numbers of the reactants change. A reduction is ___________________

                        ____________________; an oxidation  is ______________________

                        ___________________.

                        The reaction          2 H+         =     H2    is a   half-_________________

                        The reaction          Fe            =    Fe2+  is a  half-__________________
 
 
 

                Formulas:         Write the formulas for the following compounds:

                            vinegar =  5% solution of acetic acid  = ________________

                            hydrogen peroxide =   3 % solution of  ________________

                            tannic acid =  large molecule containing the benzene group _____________
                                    ( see textbook) ; it is water soluble and precipitate proteins from
                                    solution. In adding milk to tea, the tannins and milk proteins react and
                                    this results in neutralization of the astringent taste of the tea.
 

Evidence   :  now that you have done this extra effort, you are entitled to earn an additional 15 pts
                     on your participation grade ( about one point on grand total) IF

                        ----you bring your report in class on or before may the 18 th.

                        ----your answers are correct

                        ---- you write with your homemade black ink and a cotton swab the name of
                                your favorite chemistry demonstration!
 
 
 
 
 
 

                        ________________________________________________________________
                                                          favorite chemistry demonstration