CHEM 1314 H
Midterm Exam #2, 2010
In terms of the postulates and conclusions of the kinetic molecular theory of gases, give a
interpretation of each of the following experimental observations:
The volume of a gas at fixed pressure increases proportionally with the temperature.
For a fixed volume and temperature, the total pressure of a mixture of one mole of
oxygen and one mole of nitrogen is equal to the total pressure of two moles of nitrogen.
The temperature of a gas can be raised by heating it with a flame or by stirring it with a
For a fixed volume and temperature, the pressure exerted by a mole of gas with strong
intermolecular attractions is significantly less than the pressure exerted by a mole of gas
with weaker intermolecular attractions.
One mole of gas A occupies the same volume as one mole of gas B (at the same
temperature and pressure), even if the molecules of compounds A contain many more
atoms than do the molecules of compound B.
Increasing T increases average speed, resulting in greater force of collisions of particles
with walls. If resisting pressure is fixed, the pressure due to collisions will push back
container walls, thus expanding volume.
Force generated by a particle colliding with a wall depends on kinetic energy, not mass or
chemical character. Thus, pressure of two moles is independent of what molecules those
particles are, because there are no interactions.
Temperature is a measure of kinetic energy. Molecules can be accelerated thermally or
When molecules attract each other, they experience a decelerating force as they approach
the walls. This lowers the force of impact, lowering the observed pressure.
5 points each
In an ideal gas, the particles are at great distances from one another. At these distances, the
sizes of the molecules are insignificant, so differences in sizes are irrelevant.