Question

Which of the following is a synthetic indicator?

• A. Turmeric
• B. Litmus paper
• C. Methyl orange
• D. Red cabbage

Hint:

In titrations: Methyl orange is preferred for strong acid–weak base reactions, while phenolphthalein is used for strong base–weak acid reactions.

Answer 1

The Correct Option is C

Step 1: Conceptual Background:
Indicators are substances that change color in acidic or basic solutions, helping identify the pH of a solution. They are classified as:
Natural indicators: Obtained from plants (e.g., turmeric, red cabbage, litmus).
Synthetic indicators: Man-made in laboratories (e.g., phenolphthalein, methyl orange, methyl red).
Step 2: Analysis of Options:
(A) Turmeric $\rightarrow$ Natural indicator, turns red in base.
(B) Litmus paper $\rightarrow$ Natural indicator obtained from lichens.
(C) Methyl orange $\rightarrow$ Synthetic indicator, orange in neutral, red in acid, yellow in base.
(D) Red cabbage $\rightarrow$ Natural indicator, shows a variety of colors depending on pH.
Step 3: Detailed Explanation:
Since methyl orange is lab-made and widely used in titrations to detect endpoints, it qualifies as a synthetic indicator.
Step 4: Final Answer:
The synthetic indicator among the given options is Methyl orange.