Why must we add sodium bicarbonate (NaHCO3) to DCPIP/DPIP indicator (Dichlorophenol indophenol)when titrating juice for Vitamin C?
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Adding sodium bicarbonate (NaHCO3) to DCPIP/DPIP indicator when titrating juice for Vitamin C serves several purposes:
1. Maintaining an alkaline environment: DCPIP/DPIP is a redox indicator that changes color from blue to colorless when it reacts with Vitamin C. However, this reaction occurs more efficiently in an alkaline environment. By adding sodium bicarbonate, we can create a basic solution that promotes the redox reaction between DCPIP/DPIP and Vitamin C.
2. Stabilizing the pH: Sodium bicarbonate acts as a pH buffer, preventing significant changes in pH during the titration process. This ensures the reaction proceeds at a consistent rate and produces reliable and accurate results.
3. Removing other reducing agents: Juice contains various naturally occurring reducing agents apart from Vitamin C, which could interfere with the titration. Sodium bicarbonate helps in neutralizing or removing these interfering substances, allowing for selective and accurate detection of Vitamin C.
Overall, adding sodium bicarbonate ensures an optimal reaction environment, stabilizes the pH, and helps eliminate interference from other reducing agents, resulting in a more precise determination of Vitamin C content in the juice sample.
When titrating juice for Vitamin C, we use an indicator called DCPIP (Dichlorophenol indophenol). DCPIP is a blue-colored compound that turns colorless when it reacts with Vitamin C. Sodium bicarbonate (NaHCO3), also known as baking soda, is added to the DCPIP solution for a specific reason.
The addition of sodium bicarbonate serves two purposes:
1. Adjusting the pH: Sodium bicarbonate is a weak base, and it helps to maintain a basic pH for the titration reaction. The reaction between DCPIP and Vitamin C depends on the pH being basic. Without sodium bicarbonate, the DCPIP solution may not have the optimal pH for the reaction to occur effectively.
2. Enhancing the reaction: Sodium bicarbonate reacts with the acidic components present in the juice, such as citric acid, malic acid, etc. These acidic components may interfere with the reaction between DCPIP and Vitamin C, leading to inaccurate results. Adding sodium bicarbonate neutralizes these acids, allowing the DCPIP-Vitamin C reaction to proceed without any interference.
To get the answer to why sodium bicarbonate is added to DCPIP when titrating juice for Vitamin C, we need to understand the properties of DCPIP, the reaction it undergoes with Vitamin C, and the role of sodium bicarbonate in adjusting the pH and enhancing the reaction.
The indicator does not work well in an acid medium. NaHCO3 is used as a buffer to maintain an alkaline pH of about 9. For more information, see the link below:
http://www.cforyourself.com/Overview/Primer/Chemistry/c_tests.html