Q1: In a titration involving weak acid and strong base, the preferred indicator is

ANS:B - Phenolphthalein

In a titration involving a weak acid and a strong base, the preferred indicator is phenolphthalein. Explanation:

• Phenolphthalein is commonly used as an indicator in titrations involving weak acids and strong bases because of its suitable pH range for this type of reaction.
• Phenolphthalein undergoes a color change in the pH range of approximately 8.2 to 10.0. In this range, the weak acid has been neutralized by the strong base, and the solution becomes basic.
• At the beginning of the titration, when the solution is acidic (prior to the addition of the strong base), phenolphthalein remains colorless.
• As the titrant (the strong base) is added and neutralizes the weak acid, the solution reaches the pH range where phenolphthalein changes color, typically turning pink or fuchsia.
• This color change indicates the endpoint of the titration, where the stoichiometric equivalence point has been reached, and all of the weak acid has been neutralized by the strong base.

While methyl orange and ethyl orange are also indicators commonly used in acid-base titrations, phenolphthalein is preferred for titrations involving weak acids and strong bases due to its suitable pH range for this specific reaction. Fehling's solution, on the other hand, is not an indicator but rather a reagent used for the detection of reducing sugars.