Number of Indicators for Titration of Strong Acid and Strong Base: 2

Introduction:
In the process of titration, indicators are used to determine the endpoint of the reaction. Indicators are substances that undergo a color change at a specific pH value. They are added to the reaction mixture and help in visually identifying when the reaction is complete. In the case of titration between a strong acid and a strong base, there are specific indicators that are suitable for this type of reaction.

Indicators for Titration of Strong Acid and Strong Base:
Among the given indicators, the number of indicators that can be used in the titration of a strong acid and strong base is 2. These indicators are:

1. Phenolphthalein:
Phenolphthalein is a commonly used indicator in acid-base titrations. It is colorless in acidic solutions and turns pink or magenta in basic solutions. Phenolphthalein is suitable for the titration of strong acids and strong bases because the color change occurs in the pH range of 8.2 to 10.0, which is close to the neutral pH range. This indicator is widely used in titrations involving strong acids and strong bases due to its clear and distinct color change.

2. Methyl Orange:
Methyl orange is another indicator that can be used in the titration of strong acid and strong base. It is red in acidic solutions and turns yellow in basic solutions. Methyl orange is suitable for this type of titration because the color change occurs in the pH range of 3.1 to 4.4, which is close to the neutral pH range. This indicator is particularly useful when titrating strong acids and strong bases with a pH range closer to the acidic side.

Explanation:
The reason why only these two indicators are suitable for the titration of strong acid and strong base lies in their pH ranges of color change. In the case of strong acids and strong bases, the pH at the equivalence point is very close to neutral (pH 7). Therefore, indicators that produce a color change in the pH range close to neutral are ideal for this type of titration. Phenolphthalein and methyl orange fall within this range, which makes them suitable indicators for the titration of strong acid and strong base.

Conclusion:
In conclusion, among the indicators provided (phenolphthalein, methyl orange, blue litmus, and red litmus), only phenolphthalein and methyl orange can be used for the titration of a strong acid and strong base. These indicators have pH ranges of color change that are close to neutral, making them suitable for this type of titration.