Titration of 7up lab report

Experiment 12 How Acidic is it Really?: A lesson on Titration & Acids and Bases PURPOSE Students will be able to… • Determine the acidity in various samples using a pH meter and titration methods • Calculate the concentration of citric acid in clear drinks • Determine the percent by mass of acid in various drink samples • Compare and contrast the acidity of various food and drink samples BACKGROUND Table 1. Acid and sugar content of various drinks. Source: Minnesota Dental Association, retrieved from http://www.dentalgentlecare.com/diet_soda.htm Acids are added to commercial “pop” (or soda for those not from western New York) to create a “tart” taste. In colorless pop such as 7-up or Sprite, citric acid is commonly used whereas phosphoric acid is commonly used in pops such as Pepsi, Coca-Cola, or Mr. Pibb, to impart the “tart” taste. In addition, caramel is added to Pepsi, Coca-Cola, etc to produce the dark, brown color. Product Pure Water Barq's Diet 7-Up 7-Up Sprite Diet Dr. Pepper Diet Coke Mountain Dew Surge Gatorade Dr. Pepper Hawaiian Fruit Punch Orange Minute Maid Coke Classic Pepsi BATTERY ACID Acid 7.00 (neutral) 4.61 3.67 3.79 3.42 3.41 3.39 3.22 3.02 2.95 2.92 2.82 2.80 2.63 2.49 1.00 Sugar per 12 oz 0.0 10.7 tsp. 0.0 12.6 tsp. 9.0 0.0 0.0 11.0 tsp. 10.0 3.3 tsp 9.5 10.2 11.2 9.3 tsp. 9.8 tsp. 0.0 Each American consumes on average more than 46.4 gallons of pop every year, which is approximately 495 twelve oz cans (Jain, Nihill, Sobkowski, & Agustin, 2007)! This concerns health professionals because consumption of acidic beverages has been linked to erosion of tooth enamel and to calcium loss in bones. The acidity of several drinks can be found in the table above. Health professionals are also now becoming concerned with sports drinks and energy drinks like Gatorade and Red Bull as these drinks are also very acidic and are causing tooth decay (Picard, 2005). In this experiment, you will utilize the common technique of titration to quantitatively determine the acid content of a commercial pop or sports drink and compare your results among your class. You will use the acid-base indicator phenolphthalein to signal 1 the endpoint of the titration. This endpoint of the titration corresponds to the equivalence point of the reaction: the point when exactly enough of one reactant (a base, NaOH) has been added to consume all of the second reactant (an acid, citric acid) (Purdue University Laboratory Manual, Fall 2004). The chemical reaction that takes place in the titration procedure of a colorless pop or sports drink is represented by the following chemical reaction: citric acid + sodium hydroxide → sodium citrate + water H3C6H5O7 (aq) + 3 NaOH (aq) → Na3C6H5O7 (aq)+ 3 H2O (l) H H H C CO2H HO C CO2H H C CO2H + NaOH H C CO2- Na+ H2O NaOH HO C CO2- Na+ + H2O NaOH H C CO2- Na+ H2O H H PRE-LAB QUESTIONS 1. Explain in detail and show your calculations as to how you will make 100.0 mL of 0.125 M NaOH from the 1.250 M stock solution. 2. You could also make 100.0 mL of 0.125 M NaOH solution from solid sodium