key term - Bromocresol green

Definition

Bromocresol green is a pH indicator commonly used in acid-base titrations, which changes color based on the pH level of a solution. It appears yellow in acidic solutions (pH below 4.7) and turns blue in alkaline solutions (pH above 5.4), making it useful for determining the endpoint of titrations involving strong acids and bases. Its distinctive color change helps visualize the transition from acidic to neutral to basic conditions during titration.

5 Must Know Facts For Your Next Test

1. Bromocresol green is effective in a pH range of approximately 4.7 to 5.4, making it suitable for titrations involving weak acids and strong bases.
2. The color transition of bromocresol green from yellow to blue occurs around its pKa value of about 4.7, where half of the indicator molecules are protonated.
3. In practice, bromocresol green is frequently used in biological applications, such as measuring the pH of culture media or biological samples.
4. It is synthesized from brominated cresol and is part of a larger group of brominated phenolic compounds that serve as indicators.
5. While bromocresol green is widely used, its limitations include interference with certain colored solutions, which can affect color perception during titrations.

Review Questions

• How does bromocresol green function as a pH indicator during titrations, and what are its color changes?
  • Bromocresol green functions as a pH indicator by changing color depending on the acidity or alkalinity of the solution it is in. It appears yellow when the pH is below 4.7, indicating acidic conditions, and shifts to blue as the pH rises above 5.4, indicating alkaline conditions. This color change helps identify the endpoint during acid-base titrations, providing a visual cue when transitioning from acidic to neutral to basic environments.
• Discuss the practical applications of bromocresol green in laboratory settings and any potential limitations it may have.
  • Bromocresol green is commonly used in laboratory settings for acid-base titrations and pH measurements due to its clear color change within its effective range. It is particularly useful in biological applications where monitoring pH is crucial, such as analyzing culture media. However, one limitation is that its effectiveness can be hindered by colored solutions, which may obscure the color change, making it challenging to accurately determine the endpoint during titrations.
• Evaluate the significance of using bromocresol green in educational labs for teaching acid-base chemistry and how it enhances student understanding.
  • Using bromocresol green in educational labs for teaching acid-base chemistry significantly enhances student understanding by providing a clear visual representation of pH changes during titrations. This visual feedback allows students to grasp concepts like endpoints and pH scale behavior more intuitively. Moreover, engaging students with practical experiments using this indicator fosters hands-on learning experiences, enabling them to connect theoretical knowledge with real-world applications in chemistry.

Related terms

pH Indicator: A substance that changes color in response to changes in pH, used to visually represent the acidity or alkalinity of a solution.

Titration: A laboratory technique used to determine the concentration of a substance in a solution by adding a volume of titrant of known concentration until the reaction reaches its endpoint.

Endpoint: The point in a titration at which the reaction is complete, often indicated by a color change of an indicator.