The Primary Purpose of this Experiment is to Determine the Percent Content of Acetic Acid in a Household Bottle of President’s Choice Vinegar, using Titration Techniques. In addition, a Secondary Purpose for this Experiment that Derives Directly from the Primary Purpose is to Gain Hands On Experience in Titration Techniques, as a Vital Tool in our Quest to Understanding the Chemical Aspect of the World around Us.
Conducting a Titration is the Process of Applying a Balanced Chemical Equation to Determine the Volume of a Solution with an Unknown Molarity or Concentration that is Need to React with a Pre-Determined Amount of a Second Solution of a Known Molarity and Concentration. In order to Achieve a Proper Titration, however, a great deal of measuring, preparation, and precision was required from me; beginning with arranging the equipment so that the Stop Cock Tip of the Test Tube located in the Elevated Clamp Handle is located approximately one to two centimeters above the beaker where the Color Change in the Titration Indicator, in this case Phenolphthalein, is to be observed. I then proceeded to Pour and Measure 9.9 mL of 0.5 Sodium Hydroxide Solution, taking care to allow a few drops of the Sodium Hydroxide Solution to drip into the Beaker, in order to Ensure a More Accurate Reading of the Volume of Solution Used Once the Experiment was Preformed.
Once the Beaker was rinsed with Distilled water and the Initial Volume of Sodium Hydroxide was Recorded, the Experiment proceeded by Pouring and Measuring 5 mL of President’s Choice Vinegar into the Beaker and Subsequently adding two drops of the Titration Indicator, Phenolphthalein to the Beaker. Now Came the Reaction Portion of the Experiment, where I took care to Open the Stopcock with Such a Steady Flow that it would Add Only One Drop of Sodium Hydroxide ever Two to Three Seconds, while Simultaneously Counting and Keeping Track of How Many Drops of Sodium Hydroxide had been placed into the Beaker. Once, I observed a slight color change, I closed the Stopcock and Gently Swirled the Sample to Observe if the Color Change Remained. If it did not Remain, I Carefully Reopened the Stop Cock with a Steady Flow; I basically repeated this last step until the Color Change Remained for at least 30 seconds, making sure to achieve a balance of not over titrating, where too much sodium hydroxide has been added to achieve the color change nor under titrating, where too little sodium hydroxide had been added to the solution and the color change reaction did not remain for a significant amount of time.
Finally, I Recorded the Final Volume of Sodium Hydroxide Solution and Calculated How Much Sodium Hydroxide was Utilized to Create this Reaction. I then repeated this Titration Process for Two More Trials, and Disposed of the Waste Down My Kitchen Sink, Taking care to Clean All My Equipment and Dispose of any Additional Acids and Bases by Running the Faucet for Three to Four Minutes after Pouring these Solutions down the Drain.
Data Table: Quantity of NaOH Needed to Neutralize 5 mL of President’s Choice Vinegar
Initial NaOH Reading Final NaOH ReadingVolume of NaOH Used
Trial One9.9 mL1.9 mL8.0 mL
Trial Two9.9 mL2.1 mL7.8 mL
Trial Three9.8 mL1.9 mL7.9 mL
Average Volume of NaOH Used in Three Trials: 7.9 mL
1. Calculate the Average Number of mL of NaOH Used for the Three Trials and Record. (8.0 mL + 7.8 mL + 7.9 mL) = 7.9 mL of NaOH
2. Calculate the Normality of the Vinegar using the Previously Given Equation. Na= (Nb) (Volume b)
1 mol of NaOH= 40 g NaOH
1 mmol of NaOH= 0.04 g NaOH
Na= (0.5 mmol/mL) * (7.9 mL of NaOH)
Na= 0.79 mmol/mL of HC2H3O2
3. Calculate the Mass of the Acetic Acid in Grams Using the Previously Given
Equation. Mass a= (Na) (GMWa)
1 mol of HC2H3O2= 60 grams
1 mmol of HC2H3O2= 0.06 grams
= (0.79 mol/L) * (60 g/mol) *Molarity has the Same Value as mmol/mL and mol/L = 47.4 g/L= Mass a Therefore, No Need for Conversion
4. Calculate the Percentage of Acetic Acid Using the Previously Given Equation. Percent of Acetic Acid= 47.4 g/L * 100%
1000 grams/L =4.74% Percent Composition of Acetic Acid in President’s Choic Household Vinegar
A. What is the Average Percent Acetic Acid in Your Vinegar Sample? How does this Compare with the Percent Value Stated on the Vinegar Bottle Label? The Percent Composition of Acetic Acid Recorded in this Experiment for the President’s Choice of Household Vinegar was on Average 4.74%, which is Slightly Lower than the Amount Recorded on the Label of the Vinegar Bottle, which Stated Approximately 5.0% in the Ingredients Section of the Label. B. Why is it Better to Use White Vinegar Rather than Dark Vinegar for this Titration? My Educated Deduction as to Why White Vinegar was a Better Solution to use for this Titration rather than Dark Vinegar is Because in White Vinegar the Color Change in Phenolphthalein is More Readily Observed, which Greatly Reduces the Chances of Over Titrating in Comparison to Dark Vinegar, where the Color Change is Not Readily Observed. C. Write a Balanced Chemical Equation for the Neutralization of Acetic Acid with NaOH 1 HC2H3O2 (aq) + 1 NaOH (aq) 1 NaC2H3O2 (aq) + 1 H2O (l) D.
How Would Your Results Have Differed if the Tip of the Burette was Not Filled with Sodium Hydroxide Before the Initial Volume was Recorded? If the Burette was Not Filled with Sodium Hydroxide Before the Initial Volume was Recorded then the Volume of NaOH used during the Titration would Appear to Be Greater than the Actual Amount, Since Some of the Initial Volume would Be Composed of Air, thus Increasing the Value of the Amount of NaOH Used in the Titration and Decreasing the Validity of My Results. E. How Would Your Result have Differed if You Had Over Titrated (i.e. Added NaOH Beyond the Endpoint)? If I had failed to achieve a Balance in My Titration Experiment and in Actuality Over Titrated, Meaning Adding NaOH Beyond the Endpoint, then Logically the Percent Composition of Acetic Acid Would Be Greater in My Results Since Theoretically, My Results would Have Indicated that it Took a Larger Volume of NaOH to Neutralize the Acetic Acid in Vinegar.
F. What Happens if You Don’t Wear Goggles and Get Some NaOH in Your Eyes. Sodium Hydroxide, is a Corrosive Irritant when it Comes into Contact with Live Tissue, including Moist Ocular Tissue that is Located in Your Eyes. Therefore, if any NaOH does come into Contact with Your Eyes, it is Imperative to Rinse Your Eyes with Cold Water Immediately for 15-20 Minutes. The Extent of the Damage Done to Tissues in Your Eyes, is Directly Correlated to the Length of time the NaOH is in Contact with Your Eye, Therefore, it is Strongly Suggested You Take this Matter Seriously and Seek Medical Attention. Of Course, the Most Effective Type of Safety Measures is in Fact Prevention and Wearing Goggles can Significantly Reduce Your Chances of Getting Sodium Hydroxide in Your Eyes. G. A 5.0 mL Sample of Vinegar was Titrated with 7.2 mL of 0.55 M NaOH(aq). If the Density of the Vinegar Solution is 1.00 g/mL, what is the mass percent of Acetic Acid Present?
Na= (0.55 mmol/mL) * (7.2 mL)
Na= 0.792 mmol/mL= 0.792 mol/L
Mass a= (0.792 mol/L) * (60 g/mol)
= 47.52 g/L= Mass a
Percent of Acetic Acid= 47.52 g/L *100%
=4.752% of Acetic Acid
In Conclusion, in the latter portion of the last century, Titrations have gained the Belittling Reputation of being an a Technique taught in Introductory Chemistry Courses within Universities, with little or no Practical Applications within the North American Chemical Industry. Fortunately, nothing could be further from the truth. Not only are there Real Life Applications to Titration Techniques, but Titrations themselves are Utilized in Medicine, Pharmaceuticals, and Fossil Fuels and Energy Production Plants, not to mention almost any Major Chemical Industry in North America. For instance, Pharmacists use Titration Techniques in order to achieve an accurate percent composition mixture of a compound medication which patients depend on for a wide range of ailments (i.e. Anti-Depressants, Allergy Medications, and Antihistamines etc.).
Furthermore, even Doctors apply Titrations to determine the correct proportion of different medicines in an intravenous drip. Still Not Convinced? Look inside you home, Titrations Techniques are employed in order to achieve a proper balance of pH, concentration of ammonia and nitrates, as well as a range of physical and chemical conditions that are vital for the survival of your Goldfish or any other marine life kept in an aquarium. Therefore, throughout this Experiment I discovered How to Meticulously and Accurately Conduct a Titration, in order to Achieve a Balance Between Over Titrating and Under Titrating, and Produce Accurate Results of a Percent Composition of an Unknown First Solution Knowing the Molarity and Concentration of a Predetermined Second Solution, which I am absolutely Certain will Serve Me Well in My Future Chemical Caree