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Chemistry Question 70 – JEE-MAIN 2026

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Given below are two statements: Statement I: Sodium dichromate and potassium dichromate are classified as primary standards in titrimetric analysis. Statement II: Phenolphthalein is a weak base, therefore it dissociates in acidic medium. In the light of the above statements, choose the correct answer from the options given below

Recall the characteristics of a primary standard, such as high purity, stability, and non-hygroscopic nature.

Step 1: Evaluate Statement I: Primary Standards✦ Active

A primary standard must be highly pure, stable, non-hygroscopic, and have a high equivalent weight. Potassium dichromate (K2Cr2O7) meets these criteria and is widely used as a primary standard in redox titrations. However, sodium dichromate (Na2Cr2O7) is hygroscopic (absorbs moisture from the air), which makes it unsuitable as a primary standard because its exact concentration cannot be accurately determined by weighing. Therefore, Statement I is false.

Step 2: Evaluate Statement II: Phenolphthalein○ Expand

Phenolphthalein is an acid-base indicator that is a weak acid, not a weak base. Its dissociation equilibrium can be represented as HIn⇌H++In−, where HIn is the colorless acidic form and In− is the pink basic form. According to Le Chatelier's principle, it dissociates more in a basic medium (due to the consumption of H+ ions), shifting the equilibrium to the right and producing the pink In− form. In an acidic medium, the equilibrium shifts to the left, favoring the undissociated colorless HIn form. Therefore, Statement II is false.

Step 3: Determine the Correct Option○ Expand

Since both Statement I and Statement II are false, the correct option is the one that states both statements are false.

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