Q 1 :

An indicator ‘X’ is used for studying the effect of variation in concentration of iodide on the rate of reaction of iodide ion with ${\mathrm{H}}_2{\mathrm{O}}_2$ at room temperature. The indicator ‘X’ forms blue-colored complex with compound ‘A’ present in the solution. The indicator ‘X’ and compound ‘A’ respectively are              [2023]

• Starch and iodine

   

• Methyl orange and ${\mathrm{H}}_2{\mathrm{O}}_2$

   

• Methyl orange and iodine

   

• Starch and ${\mathrm{H}}_2{\mathrm{O}}_2$

   

Q 2 :

Incorrect statement for the use of indicators in acid–base titration is:             [2023]

• Methyl orange may be used for a weak acid vs weak base titration.

   

• Phenolphthalein may be used for a strong acid vs strong base titration.

   

• Methyl orange is a suitable indicator for a strong acid vs weak base titration.

   

• Phenolphthalein is a suitable indicator for a weak acid vs strong base titration.

   

Q 3 :

Given below are two statements:

Statement I: In redox titration, the indicators used are sensitive to change in pH of the solution.

Statement II: In acid–base titration, the indicators used are sensitive to change in oxidation potential.

In the light of the above statements, choose the most appropriate answer from the options given below.                 [2023]

• Statement I is incorrect but Statement II is correct.

   

• Statement I is correct but Statement II is incorrect.

   

• Both Statement I and Statement II are incorrect.

   

• Both Statement I and Statement II are correct.

   

Q 4 :

Given below are two statements:

Statement I: Methyl orange is a weak acid.

Statement II: The benzenoid form of methyl orange is more intense/deeply coloured than the quinonoid form.

In the light of the above statements, choose the most appropriate answer from the options given below:                    [2023]

• Statement I is incorrect but Statement II is correct

   

• Both Statement I and Statement II are correct

   

• Statement I is correct but Statement II is incorrect

   

• Both Statement I and Statement II are incorrect

   

Q 5 :

The titration curve of weak acid vs. strong base (with phenolphthalein as indicator) is shown below. The $K_{\text{phenolphthalein}}=4\times {10}^{-10}$.

Given: $\text{log 2}=0.3$

The number of following statement/s which is/are correct about phenolphthalein is __________.                [2023]

A. It can be used as an indicator for the titration of weak acid with weak base.

B. It begins to change colour at pH = 8.4

C. It is a weak organic base

D. It is colourless in acidic medium