Question

Which of the following statement is false?

• A. Reducing agents often cause fading of dyes
• B. Anionic dyes are the most stable at acid pHs
• C. Basic dyes are not sensitive to alkalies
• D. Cationic dyes may be precipitated by soaps and clays

Answer 1

The Correct Option is B

Let's analyze each of the given statements to determine which one is false:

1. Statement: "Reducing agents often cause fading of dyes"
   • Explanation: Reducing agents can indeed cause fading because they reduce the chromophore of the dye, which results in loss of color. This process is common in chemical fading of fabric dyes.
   • Verdict: True. Reducing agents often cause fading of dyes.
2. Statement: "Anionic dyes are the most stable at acid pHs"
   • Explanation: Anionic dyes, which are negatively charged, are typically more soluble and stable in alkaline conditions rather than acidic conditions. Acid conditions can lead to the protonation of these dyes, reducing stability.
   • Verdict: False. Anionic dyes are not the most stable at acid pH; they are more stable in alkaline conditions.
3. Statement: "Basic dyes are not sensitive to alkalies"
   • Explanation: Basic dyes are cationic and are generally more resistant to alkaline conditions. They are more likely to interact with acidic environments due to their positive charge.
   • Verdict: True. Basic dyes are generally less sensitive to alkalies.
4. Statement: "Cationic dyes may be precipitated by soaps and clays"
   • Explanation: Cationic dyes have a positive charge and can form insoluble precipitates in the presence of negatively charged species like soaps and clays, which have anionic characteristics.
   • Verdict: True. Cationic dyes can be precipitated by soaps and clays.

Based on the examination of each statement, the false statement is:

Correct Answer: "Anionic dyes are the most stable at acid pHs"