SAT Subject Physics Practice Question 417: Answer and Explanation

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Question: 417

8. The volume of an ideal gas is reduced to half its original volume. The density of the gas

A. remains the same.
B. is halved.
C. is doubled.
D. is tripled.
E. is quadrupled.

Correct Answer: C


The correct answer is (C). The same number of gas particles now occupies half the volume. The formula for density is d = m/v where mass can be restated as the mass of the gas = (mol. Mass) (Avogadro's Number). Thus the mass is directly related to the number of particles in the space. More particles in less space yield greater density.

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