Which one of the following can be used as an acid base indicator by a visually impared student ?

Options

A. Litmus
B. Turmeric
C. Vanilla essence
D. Petunia leaves

Explanation

To solve the question of which acid-base indicator can be used by a visually impaired student, we can follow these steps:

### Step 1: Understand the Role of Acid-Base Indicators
Acid-base indicators are substances that change color in response to the acidity or basicity of a solution. Common indicators include litmus, phenolphthalein, and turmeric, which typically rely on color changes that are visible to the eye.

**Hint:** Indicators are usually visual, but some can be detected through other senses.

### Step 2: Consider the Needs of a Visually Impaired Student
Since the student is visually impaired, they will not be able to rely on color changes to determine whether a solution is acidic or basic. Therefore, we need to consider indicators that can be detected using other senses.

**Hint:** Think about how other senses, like smell, could be used to identify acid-base properties.

### Step 3: Identify Alternative Indicators
Among the common indicators, vanilla essence is noted as an olfactory indicator. An olfactory indicator is one that can be detected through smell rather than sight. This means that a visually impaired student could use the smell of vanilla essence to determine the acidity or basicity of a solution.

**Hint:** Look for indicators that provide information through smell rather than sight.

### Step 4: Conclusion
Given the options, the best choice for a visually impaired student would be vanilla essence, as it serves as an olfactory indicator.

**Final Answer:** The correct answer is C, vanilla essence.

### Summary of Steps:
1. Understand what acid-base indicators are.
2. Consider the limitations of a visually impaired student.
3. Identify indicators that can be used through senses other than sight.
4. Conclude that vanilla essence is the appropriate choice.