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Titration Comparison Between

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					Titration Comparison Between
     Two Vinegar Brands




                                Aj Klatch
                                Kyle Tisi
                           AP Chemistry
                          Mr. Edmondson
                                   3/4/02
                                      2/3
                                                                                       2


I.   Abstract

                The purpose of this laboratory experiment was to compare the

        percent concentrations of acids among an expensive and an inexpensive

        vinegar using phenolphthalein as the indicator.

                The titration data that was achieved for the cheap vinegar with a

        constant 15ml of vinegar used is as follows. For titration 1, neutralization

        took 29.80ml of .5M NaOH. For titration 2, neutralization took 29.00ml

        of .5M NaOH. For titration 3, neutralization took 29.60ml of .5M NaOH.

        From this data we were able to determine the percent of acetic acid in the

        vinegar. For titration 1, the percent of acid was 5.86%. For titration 2, the

        percent of acid was 5.70%. For titration 3, the percent of acid was 5.82%.

                The titration data that was achieved for the expensive vinegar with

        a constant 15ml of vinegar used is as follows. For titration 1,

        neutralization took 26.80ml of .5M NaOH. For titration 2, neutralization

        took 28.20ml of .5M NaOH. For titration 3, neutralization took 28.00ml

        of .5M NaOH. From this data we were able to determine the percent of

        acetic acid in the vinegar. For titration 1, the percent of acid was 5.27%.

        For titration 2, the percent of acid was 5.55%. For titration 3, the percent

        of acid was 5.44%.

                The statistics data for the cheap acid gave us an S.D.M. value of

        .080 and an average of 5.76%. Our percentage of error when compared to

        the mean value was .35%.
                                                                            3


       The statistics data for the expensive acid gave us an S.D.M. value

of .067 and an average of 5.61% acetic acid in the vinegar. Our

percentage of error when compared to the mean value was 3.03%.
                                                                                     4


               Titration Comparison Between
                    Two Vinegar Brands


II.    Materials
        1. Finest Vinegar
        2. Heinz Vinegar
        3. Phenolphthalein Solution
        4. Distilled Water
        5. Sodium Hydroxide Solution

III.   Apparatus
        1. Two 150 ml beakers
        2. Two burets
        3. Clamp
        4. Double buret
        5. Flask
        6. Ring stand
        7. Wash bottle

IV.    Procedure
         1. Gathered materials.
         2. Placed approximately 100-ml of the Heinz and Finest vinegars in seperate
           150-ml beakers.
         3. Poured a 10-ml portion of the Heinz vinegar into a buret.
         4. Poured the 10-ml portion of Heinz vinegar into a 50-ml flask of distilled
           water.
         5. Put three drops of phenolphthalein solution in with the Heinz vinegar and
           distilled water.
         6. Titrated the vinegar with the sodium hydroxide while swirling and
           washing down the flask frequently.
         7. Waited until the vinegar turned to a light pink color then turned off the
           stopcock and calculated the data.
         8. Discarded the liquid in the flask and rinsed thoroughly with distilled
           water, then ran two more titrations after the first.
         9. Calculated the normality after each trial then averaged their calculations
           for the normality of the Heinz vinegar.
        10. Repeated same procedure three times for the Finest vinegar.
                                                                                     5


    V.    Data
          a. Class Statistics – Cheap Acid
X            M              R |(x-m)| R2         Ө = (ε R2/(N-     S.D.M. (Ө/N1/2)
                                                 1))1/2
6.05         5.76            .29      .084       .18               .080
5.74                         .020     .00040
5.68                         .080     .0064
5.75                         .010     .00010
5.57                         .19      .036


          b. Class Statistics – Expensive Acid
X            M              R |(x-m)| R2         Ө = (ε R2/(N-     S.D.M. (Ө/N1/2)
                                                 1))1/2
5.63         5.61            .020     .00040     .15               .067
5.44                         .17      .029
5.77                         .16      .026
5.72                         .11      .012
5.48                         .13      .017


          c. Cheap Acid – Data

                     Trial 1                 Trial 2             Trial 3
Volume of Acid       15.00ml                 15.00ml             15.00ml
Volume of Base       29.80ml                 29.00ml             29.60ml
Normality of NaOH    .50                     .50                 .50
% Acetic Acid        5.86%                   5.70%               5.82%



          d. Expensive Acid - Data

                     Trial 1                 Trial 2             Trial 3
Volume of Acid       15.00ml                 15.00ml             15.00ml
Volume of Base       26.80ml                 28.20ml             28.00ml
Normality of NaOH    .50                     .50                 .50
% Acetic Acid        5.27%                   5.55%               5.44%

          e. Percent Error

Finast: .02/5.76 * 100% = .35% Compared to Class
Heinz: .17/5.61 * 100% = 3.03% Compared to Class
                                                                                          6


   VI.    Math
          a. Stoichiometry
Molarity=Moles/Volume(L)
.5M NaOH=X/.00185L NaOH
X=.00925 mol NaOH
.00925mol NaOH * 1mol HC2H3O2/1mol NaOH=.00925mol HC2H3O2
.00925mol HC2H3O2/.005L = .185M HC2H3O2
          b. statistics
                  i. M (mean)

Mean = Summation of all the X numbers Divided by number of X
Example: (.49 + .75 + .78 + .85 + .93 + .94)/6 = .79
                  ii. R (Residual)

R = |(x-m)| = Which is the absolute value of the X value minus the Mean value.
Example: .49 - .79 = -.30 = .30
                  iii.
                         R2

Simply the residual squared.
Example: R=.30 R squared = .090
                 iv. Ө

Ө = (ε R2/(N-1))1/2 = which is the sum of the residual squared divided by the number of
samples minus one square-rooted.
Example: ((.090+.0016+.00010+.0036+.020+.023)/5)1/2 = .166
                   v. S.D.M.

S.D.M. = Standard Deviation of the Mean = (Ө/N1/2) = Sigma/The square-root of the
number of samples.
Example: .166/61/2
          c. Percent Error
                   i. %Error = |actual-theoretical|/actual * 100%
                  ii. ex: .17/5.61 * 100% = 3.03%
                                                                                         7


VII.   Conclusion

                 In closing, this laboratory experiment was based on a weak acid

          strong base principle. Since the acid was weak, the equilibrium would be

          shifted more towards a higher pH, thus, requiring the use of

          phenolphthalein as an appropriate indicator since phenolphthalein

          indicates change at roughly a pH of 8.1. The reason for this is because of

          the disassociation constant for acetic acid which is large, thus, revealing

          that it will not disassociate as quickly as a strong acid making it a weaker

          electrolyte by default. What would happen in this experiment as more

          base would be added to the solution is that the equilibrium will gradually

          shift to a high pH indicating a color change and then fade away back to

          clear. This is because the base is slowly “breaking down” the acid further

          and then forming more water and Sodium Acetate causing neutralization

          again and allowing the pH to drop more prevalently towards the

          equilibrium.

                 As stated earlier, the disassociation is never complete for the weak

          acetic acid in this experiment, therefore, the equilibrium position that

          would be considered 7 with a strong acid is now considered roughly 8.1

          making the phenolphthalein the prime detection agent rather then

          Bromthymol Blue in a reaction such as this.

                 Again our data for this lab is as follows. The titration data that was

          achieved for the cheap vinegar with a constant 15ml of vinegar used is as

          follows. For titration 1, neutralization took 29.80ml of .5M NaOH. For
                                                                               8


titration 2, neutralization took 29.00ml of .5M NaOH. For titration 3,

neutralization took 29.60ml of .5M NaOH. From this data we were able to

determine the percent of acetic acid in the vinegar. For titration 1, the

percent of acid was 5.86%. For titration 2, the percent of acid was 5.70%.

For titration 3, the percent of acid was 5.82%.

       The titration data that was achieved for the expensive vinegar with

a constant 15ml of vinegar used is as follows. For titration 1,

neutralization took 26.80ml of .5M NaOH. For titration 2, neutralization

took 28.20ml of .5M NaOH. For titration 3, neutralization took 28.00ml

of .5M NaOH. From this data we were able to determine the percent of

acetic acid in the vinegar. For titration 1, the percent of acid was 5.27%.

For titration 2, the percent of acid was 5.55%. For titration 3, the percent

of acid was 5.44%.

       The statistics data for the cheap acid gave us an S.D.M. value of

.080 and an average of 5.76%. Our percentage of error when compared to

the mean value was .35%.

       The statistics data for the expensive acid gave us an S.D.M. value

of .067 and an average of 5.61% acetic acid in the vinegar. Our

percentage of error when compared to the mean value was 3.03%.

       Finally, there are numerous places where error can occur within

this lab which is why repetition was used in order to determine all of our

values. Error can be found while transferring solutions to and from

beakers, rounding during calculations to significant figures, and by visual
                                                                          9


human error itself. However, our data was relatively consistent and for

one of our acids we had an excellent .35% of error and only a 3.03% of

error for the other, thus, revealing that we completed this laboratory

experiment successfully.