Question

Assertion: Air is a mixture, not a compound.
Reason: The proportion of the constituents of air vary from place to place .Even in the same place the proportion varies from time to time .In a compound ,the proportion of different constituents always remains fixed.
A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion .
B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion .
C. Assertion is correct but Reason is incorrect.
D. Both Assertion and Reason are incorrect.

Answer 1

Hint: To solve this problem we must be very clear about how air is a mixture, we are always told that the air is a homogenous mixture of various gases, constituents of air are oxygen, nitrogen, carbondioxide and other gases. Air also contains smoke and dust. Combustion is possible due to oxygen gas and it is necessary for respiration. Carbon dioxide is essential for photosynthesis for plants and trees. The major component of air is nitrogen gas. The composition of air is never constant, it varies from place to place.

Complete step by step solution:
The proportion of the constituents is not constant, it varies from place to place .Even in the same place the proportion varies from time to time. In a compound, the proportion of different constituents always remains fixed. As we know dust and smoke is present in our atmosphere because of burning of fuel and substances. These dust and smoke particles present in air can vary from place to place and even they can vary from time to time. Water vapor is the component of the air that varies the most from place to place. Air has many gases which have different properties at different temperatures and pressures so it is not possible to have their composition always constant.
So we can conclude this problem by saying that Both Assertion and Reason are correct and Reason is the correct explanation for Assertion as assertion is correct and reason is also correct and it is explaining the assertion.

Note: We know that air is a homogeneous mixture of various gases and other substances . These gases can vary from place to place as they have their own properties at different temperature and pressure. As temperature of any place can not be constant so the proportion of the constituents of air varies from place to place .Even in the same place the proportion varies from time to time .In a compound ,the proportion of different constituents always remains fixed. Compounds are formed by following the law of constant composition