The colour of methyl orange in alkaline medium is?

Analysis of the Question

This question tests your knowledge of acid-base indicators. Indicators are substances that change color depending on the pH of the solution they are in. You are required to identify the specific color change of methyl orange when placed in an alkaline (basic) environment.

Concept Explanation

Methyl orange is a common pH indicator used in titrations. Its behavior is defined by its pH range:

• Acidic medium (pH < 3.1): It appears red.
• Transition range (pH 3.1 – 4.4): It appears orange.
• Alkaline/Basic medium (pH > 4.4): It appears yellow.

Because alkaline solutions have a pH greater than 7, methyl orange will consistently show its basic-range color in these environments.

Step-by-Step Solution

1. Identify the medium: The question specifies an "alkaline medium."
2. Recall the indicator properties: Methyl orange is known to be red in acidic conditions and yellow in basic conditions.
3. Evaluate the options: • Red is for acidic conditions. • Orange is the transition color (neutral/slightly acidic). • Yellow is for alkaline conditions.
4. Conclusion: Since the medium is alkaline, the color must be yellow.

Exam Tip

A great way to remember this is the mnemonic "MY": Methyl orange is Yellow in alkaline solutions. Also, remember that methyl orange is often used for strong acid-weak base titrations, where the endpoint color change is from yellow to red as the acid is added.