I. It has a varied composition from one place to another. ll. it constituents can be separated by physical…

To determine why air is classified as a mixture, let's analyze the properties provided in the question:

1. Analyze the Statements

• Statement I: "It has a varied composition from one place to another." A pure substance (like a compound) has a fixed, definite composition. A mixture, however, does not have a fixed ratio of components. For example, the amount of water vapor, dust, or pollutants in the air varies depending on your location (e.g., near the sea vs. in a dry desert). This is a characteristic property of a mixture.

• Statement II: "Its constituents can be separated by physical means." This is the fundamental definition of a mixture. The components of air (nitrogen, oxygen, argon, etc.) can be separated using physical processes like fractional distillation of liquid air. Since no chemical reaction is required to separate them, this confirms air is a mixture.

• Statement III: "It contains unreactive noble gases." While it is true that air contains noble gases like argon and neon, this statement describes the composition of air, not the nature of it being a mixture. Many compounds also contain various elements, but that doesn't make them mixtures. Therefore, this statement does not prove that air is a mixture.

2. Conclusion

Statements I and II are the specific characteristics that define air as a mixture. Statement III is merely a factual observation about what is found inside the air, but it does not serve as evidence for the classification of "mixture."

3. Identify the Answer

Based on the analysis, the correct options are I and II.

Exam Tip: Always remember the "Golden Rule" for mixtures: A mixture is a physical combination of substances that can be separated by physical methods and does not have a fixed chemical formula. If you see a question asking for proof of a mixture, look for "physical separation" or "variable composition."