Question

alt , you will use the observed solution colour change due to phenolphthalein (colourless e endpoint) to indicate the completion of each reaction. Due to the colours of the juices you will be studying, the expected colour change of colourless to pink may not be observed. For each juice, state the colour change that you will likely observe at the endpoint. Grapefruit juice Orange juice Lemon juice 3. The indicator that will be used in Part 2 is bromophenol blue. What is the colour change that you will likely observe at the endpoint for the titration of the Rolaids and Tums? 4. The structure and formula of citric acid is provided in the Background. Calculate the Molar Mass of citric acid. These

Answer 1

2. All the three given juices of grapefruit , orange and lemon are in acidic nature due to the presence of the main ingredients as organic acids like citric, malic, ascorbic acids with their combinations. These juices have the range of pH is 2.0 to 4.2.

When we analyse the colour change of the phenolphthalein indicator with the help of their titration with base solution (NaOH). As it will be the case of weak acid and strong base titration method using the phenolphthalein indicator, the following colour change of the phenolphthalein indicator is, observed at their endpoint of titration with three juices.

a) Grapefruit juice - Purple to dark pink

b) Orange juice - Orange to Pink

c) Lemon juice - Colurless to pink.

3. The main ingredient of anatacid Rolaids and Tums is calcium carbonate which has poor solubility in water at low temperature. But have good solubility in water containing CO₂ (rain water). It is the type of weak base and strong acid titration method. During such titration of Rolaids and Tums using 2-bromphenol blue as pH indicator which changes it colur from yellow to blue colour at the end point of the titration.

4. Please find the below image

НО ОН — ОН ОН Citric Acid Molecular formula =C6H2O7 Molar Mass = 192.12 g/mol