A student conducts a chemical analysis of the components of a popular soft drink. The beverage label shows that the drink contains carbonated water, phosphoric acid, caffeine, and caramel color, but does not indicate the concentrations of these chemicals.
Dissolved carbon dioxide will react reversibly with water to form carbonic acid. In an attempt to analyze the beverage composition, the student conducts the following experiments on a one liter sample of the beverage.
Experiment 1
The sample is placed in a sealed beaker cooled to 10?C and a vacuum is created in the space above the beverage. The gas pumped from this space is passed through a solution of BaCl2, producing a white precipitate. The process continues until no more precipitate forms. The precipitate is dried and found to have a mass of 9.5 grams.
Experiment 2
The remaining solution left in the sealed beaker is then titrated with 0.01 M NaOH to give the titration curve shown in Figure 1.
Figure 1
The student uses the data from Experiment 1 and Experiment 2 to calculate the initial pH of the beverage.
If a significant quantity of precipitate was lost in the drying process of Experiment 1, the calculated pH: