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General Chemistry

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Gases

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The behavior of gases can be predicted to a large extent on the basis of various laws. Gases are expressed mainly in terms of pressure, volume, and temperature. Many gases obey the ideal gas laws and those gases are called ideal gases. If we are not doing precision experiments, we can normally ignore the slight deviations that occur under normal conditions. Nevertheless, we cannot completely ignore the deviation factors.

According to Boyle's law, the pressure is inversely proportional to the volume at a constant temperature. Charles' law states that the volume is directly proportional to the temperature at a constant pressure. Combining these laws and Avogadro's law gives the combined gas law.

PV = nRT

(The ideal gas law)

Not all gases behave ideally. There are often deviations from the ideal behavior. At low temperatures, gases often behave differently apart from what is described by kinetic-molecular theory of gases. Considering these correction factors, the modified gas equation is:

The correction constants or Vander Waal constants, a and b, of gases are experimentally found. The Van der Waal constants of some gases are given in Table 1.


Table 1

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Under which of the following conditions will gases behave most ideally?

A Low temperature and high pressure
B High temperature and low pressure
C Low temperature and low pressure
D Gas behavior does not depend on temperature and pressure if the gas is an ideal gas, and such a gas will behave ideally regardless of the conditions
Ans. B Gases best behave the most ideally under conditions such as high temperature and low pressure. Choice D is wrong. The passage makes the behavior of gases very clear: They depend on the prevailing temperature and pressure.

Gases Flashcard List

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The behavior of gases can be predicted to a large extent on the basis of various laws. Gases are expressed mainly in terms of pressure, volume, and temperature. Many gases obey the ideal gas laws and those gases are called ideal gases. If we are not doing precision experiments, we can normally ignore the slight deviations that occur under normal conditions. Nevertheless, we cannot completely ignore the deviation factors. According to Boyle's law, the pressure is inversely proportional to the volume at a constant temperature. Charles' law states that the volume is directly proportional to the temperature at a constant pressure. Combining these laws and Avogadro's law gives the combined gas law. PV = nRT (The ideal gas law) Not all gases behave ideally. There are often deviations from the ideal behavior. At low temperatures, gases often behave differently apart from what is described by kinetic-molecular theory of gases. Considering these correction factors, the modified gas equation is: The correction constants or Vander Waal constants, a and b, of gases are experimentally found. The Van der Waal constants of some gases are given in Table 1. Table 1 Based on kinetic-molecular theory, which of the following are true? I. At a given temperature, all gases have the same average kinetic energy. II. At a given temperature, different gases have different average velocities. III. The average kinetic energy is proportional to the absolute temperature.A I onlyB II onlyC I & III onlyD I, II & III