Question

Which one of the following can be used as an acid-base indicator by a visually impaired (blind) student?

• A. Turmeric
• B. Vanilla essence
• C. Methyl orange
• D. Litmus

Hint:

Olfactory indicators (smell-based) for visually impaired:

• Vanilla essence \(\Rightarrow\) Smell disappears in base
• Onion \(\Rightarrow\) Smell destroyed in base
• Clove oil \(\Rightarrow\) Smell changes in acid/base

These are safer and more accessible alternatives to visual indicators.

Answer 1

The Correct Option is B

Step 1: Understand the requirement for visually impaired students.
A visually impaired student cannot rely on color change to identify acids and bases. Therefore, an indicator that produces a change detectable by other senses (like smell) is needed.
Step 2: Analyze each option.

• (A) Turmeric: Not suitable. Turmeric changes from yellow to red in bases, but this is a color change only, not detectable by blind students.
• (B) Vanilla essence: Suitable. Vanilla essence has a characteristic smell. In acids, it retains its smell, but in bases, it loses its smell. This olfactory indicator is perfect for visually impaired students.
• (C) Methyl orange: Not suitable. Methyl orange changes from red to yellow, which is a color change only.
• (D) Litmus: Not suitable. Litmus changes from blue to red (acid) or red to blue (base), which is a color change only.

Step 3: Identify olfactory indicators.
Olfactory indicators are substances whose smell changes in acidic or basic environments. Examples include:

• Vanilla essence (smell disappears in bases)
• Onion (smell is destroyed in bases)
• Clove oil

Final Answer: (B) Vanilla essence