To lesarn how to titrate chemicals in a lab. Also to be able to determine the concentration of an acetic acid solution. Purpose: To learn how to titrate, and calulate the concentration of an acetiuc acid solution. In this case the concentration of vinegar, which is diluted acetic acid. Hypothesis: The sodium hydroxide used in this titration would balance out the acetic acid in vinegar. The phenolpthalein, a acid –base color indicator will let us know the vinegar have reach a point of neutralization once the vinegar turns pink. We can then calculate the concentration of acetic acid in the vinegar.
Procedure: Data: Set up the lab: Take a tick text book and place it on top of the labpaq box to use as a titrator holder. Slip the clamp into the textbook by placing the test tube clamp into the middle of the book. The stop cock tip should be 1-2 cm above the beaker. Use the test tube holder to clamp the 10 mL syringe with an affixed stop cock twisted on a the end. The syringe and the sto pcock will ac taas your titrator. Place a 100 mL beaker next to the box/book stack, placing it under your titrator. Place a piece of white paper under your beaker to help observe the change in color.
Fill the syringe from the top with NaOH from the dropper bottle with 9-10 mL of the 0. 5 M NaOH solution. Let a few drops drip into the beaker to be sure there is no air in the tip of the titrator. Pour in drain and flush with water, wash and dry beaker to be use in the experiment Experiment: Read and record the intial volume of the NaOH solution in the titrator on your data table. Use a graduated cylinder to measure 5 mL of vinegar sample then pour it in to the 50 mL beaker. Add 2 drops of the phenolpthalein to the vinegar sample. Place the vinegar sample with phenolpthalein under the titrator.
Open the stop cock and add one drop at a time of the NaOH to the beaker. Swirl gently after each drop into the beaker and observe any change in color, continue adding a drop at t atime and swirling until the color changes to a pink or burgundy color and remains that way for at least 30 seconds. In the data table record the ending volume of the NaOH in the syringe from the titrator. Subtract the ending volume from the intial volume to know how much was used. Save the remaining NaOH in the syringe and add more if needed in order to repeat the titration two more times. Repeat step 2 to 6 two more times.
Find the average volume. Wash any content down the drainand flush with water, dry the beakers. Data: Data Table 1: Quantity of NaOH needed to Neutralize 5 mL of Acetic Acid Brand of Vinegar Used: stanrdard vinegar Label Notes: 20 mL of White Vinegar Initial NaOH reading (Interpolate to 0. 1 mL) Final NaOH reading (Interpolate to 0. 1 mL) Volume of NaOH used 9. 2 . 6 8. 6 10. 0 1. 4 8. 6 1 / 2 10. 0 1. 4 8. 6 Average volume of NaOH used: 8. 6 Conclusion: The titration took have a average volume of 8. 6 mL in order for the acetic acid in the vinegar to get neutralized. Each trial take the a total volume of 8.
6 mL total. Given a molarity of . 86 which is also equal to . 86 of normality. With that normality it give my vinegar a mass of 51. 6 g/L of acetic acid with a percentage of 5. 16 % of acetic acid in it. Close to the standard vinegar of 5% acetic acid. Calulation: Calculate the average number of mL of NaOH used for the 3 trials and record. 8. 6 mL B. Calculate the Normality of the vinegar using the previously given equation. (0. 5 M NaOH) x (8. 6 mL NaOH) / (5 mL vinegar) = . 86 M= . 86 N vinegar C. Calculate the mass of the acetic acid in grams using the previously given equation.
(0. 86 mol/L) x ( 60 g acetic acid/mol) = 51. 6 g/L acetic acid D. Calculate the percentage of acetic acid using the previously given equation. ((51. 6 g/L) x 100) / (1000 g/L) = 5. 16% Follow Up Questions: What is the average % acetic acid in your vinegar sample? Standard vinegar is 5% acetic acid. How does your result compare with the standard? I used the standard vinegar the kit hace and it should be 5%, my calulation say that my vinegar is about 5%, it is actually 5. 16% acetic acid. Why is it better to use white vinegar rather than dark vinegar for this titration?
White vinegar is better to use since it is clear it will allow you to see the change in color easier. Darker vinegar also have other chemical in it while white vinegar only have acetic acid. Write a balanced equation for the neutralization of acetic acid with NaOH. NaOH + CH3COOH NaCH3COO + H2O How would your results have differed if the tip of the burette was not filled with sodium hydroxide before the initial volume reading was recorded? I could think that there was more acetic acid in the vinegar than there really is. How would your results have differed if you had over-titrated, i. e.added NaOH beyond the endpoint?
The color your still be there after the change but the amount of volume of the NaOH record from the titration would be different and that would give us a different calulation in the result. What happens if you don’t wear goggles and get some NaOH in your eyes? It will cause discomfort and irritation to your eye even permanent damage to my vision. 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? 4. 8% POWERED BY TCPDF (WWW. TCPDF. ORG).