Acid-Base Indicators in Titrations

The video tutorial explains the use of acid-base indicators in titrations to determine equivalence points. It discusses a hypothetical indicator with color changes at different pH levels, highlighting the importance of pKa values. The tutorial also guides on selecting the right indicator for titrations, using examples like methyl red and phenolphthalein, and emphasizes matching the indicator's color change range with the equivalence point's pH.

What is the role of acid-base indicators in titrations?

• To measure the temperature of the solution

• To determine the equivalence point

• To calculate the molarity of the solution

• To neutralize the solution

In the protonated form, what color does the hypothetical indicator appear?

• Blue

• Green

• Yellow

• Red

At a pH of 2, what is the predominant form of the indicator?

• Deprotonated form

• Ionized form

• Protonated form

• Neutral form

What color does the solution appear at a pH equal to the pKa value?

• Orange

• Yellow

• Red

• Green

What is the approximate pH range over which the hypothetical indicator changes color?

• 4 to 6

• 3 to 5

• 2 to 4

• 1 to 3

Why is it important to match the pKa value of an indicator to the pH of the equivalence point?

• To ensure the solution remains colorless

• To achieve a precise color change at the equivalence point

• To increase the acidity of the solution

• To decrease the basicity of the solution

Which indicator is suitable for a weak acid-strong base titration?

• Phenolphthalein

• Methyl red

• Litmus

• Bromothymol blue

What is the pH range over which phenolphthalein changes color?

• 4 to 6

• 6 to 8

• 10 to 12

• 8 to 10

Why is methyl red not suitable for a titration with an equivalence point between 8 and 10?

• Its pKa value is too high

• Its pH range is too low

• It changes color too slowly

• It is not soluble in water

For a weak base-strong acid titration, which indicator would be a better choice?

• Phenolphthalein

• Methyl red

• Thymol blue

• Bromothymol blue