Which of the following are true for an acid- base titration?

Options

A. Indicators catalyse the acid-base reactions by releasing or accepting `H^(o+)` ions.
B. Indicators do not significantly affect the `pH` of the solution to which they are added
C. Acid-base reactions do not occur in the absence of indicators
D. Indicators have different colours in dissociated and undissociated forms.

Explanation

To determine which statements are true for an acid-base titration, we will analyze each statement provided in the question.

### Step-by-Step Solution:

1. **Statement Analysis**:
- We have four statements to evaluate. Let's analyze each one.

2. **Statement 1**: "Indicators catalyze the acid-base reaction by releasing or accepting H⁺ ions."
- **Analysis**: This statement is incorrect. Indicators do not catalyze the reaction; rather, they are substances that change color in response to the pH of the solution. They do not participate in the acid-base reaction by releasing or accepting H⁺ ions.

3. **Statement 2**: "Indicators do not significantly affect the pH."
- **Analysis**: This statement is correct. Indicators are typically weak acids or bases and do not significantly alter the pH of the solution when added in small amounts. Their primary role is to indicate the pH level through color change.

4. **Statement 3**: "Acid-base reactions do not occur in the absence of indicators."
- **Analysis**: This statement is incorrect. Acid-base reactions can occur without the presence of indicators. Indicators are merely used to observe the endpoint of the titration but are not necessary for the reaction to take place.

5. **Statement 4**: "Indicators have different colors in dissociated and undissociated forms."
- **Analysis**: This statement is correct. Many indicators exhibit different colors depending on whether they are in their dissociated (ionized) or undissociated (neutral) forms. For example, phenolphthalein is colorless in acidic solutions and pink in basic solutions.

6. **Conclusion**:
- The correct statements regarding acid-base titration are:
- Indicators do not significantly affect the pH.
- Indicators have different colors in dissociated and undissociated forms.

### Summary of True Statements:
- **True Statements**:
- Indicators do not significantly affect the pH.
- Indicators have different colors in dissociated and undissociated forms.