Examples of acid-base indicators

🧪 Quick Study Guide

• 🌈 Acid-base indicators are substances that change color depending on the pH of the solution.
• ⚗️ They are typically weak acids or bases.
• 📝 The color change occurs because the indicator's conjugate acid and base forms have different colors.
• 🌡️ The pH range over which an indicator changes color is called its transition range.
• 🧮 Common indicators include:
• $ \text{Litmus (pH 5.0-8.0)} $
• $ \text{Methyl Orange (pH 3.1-4.4)} $
• $ \text{Phenolphthalein (pH 8.3-10.0)} $
• 💡 Indicators are used in titrations to determine the endpoint of a reaction.

Practice Quiz

1. Which of the following is NOT a common acid-base indicator?
   1. Methyl Orange
   2. Litmus
   3. Phenolphthalein
   4. Sodium Chloride
2. What is the typical pH range for Litmus indicator?
   1. pH 2.0-4.0
   2. pH 5.0-8.0
   3. pH 9.0-11.0
   4. pH 12.0-14.0
3. Which indicator is commonly used in titrations involving strong acids and strong bases?
   1. Methyl Red
   2. Bromothymol Blue
   3. Phenolphthalein
   4. Litmus
4. What causes the color change in acid-base indicators?
   1. Change in temperature
   2. Change in pressure
   3. Change in pH
   4. Change in volume
5. In what type of chemical reaction are acid-base indicators most commonly used?
   1. Precipitation
   2. Redox
   3. Titration
   4. Combustion
6. Which of the following indicators has a transition range in the acidic region (pH < 7)?
   1. Phenolphthalein
   2. Methyl Orange
   3. Thymol Blue (high pH range)
   4. Alizarin Yellow
7. What is the purpose of using an acid-base indicator in a titration?
   1. To speed up the reaction
   2. To determine the endpoint of the reaction
   3. To change the color of the solution for aesthetic purposes
   4. To increase the pH of the solution