Boyle's law: P % 1/V at constant n and T In the kinetic molecular theory (KMT), P is proportional to the collision frequency which is proportional to 1/V. As the volume increases there will be fewer collisions per unit area with the walls of the container and pressure will decrease (Boyle's law). Charles's law: V % T at constant n and P When a gas is heated to a higher temperature, the velocities of the gas molecules increase and thus hit the walls of the container more often and with more force. In order to keep the pressure constant, the volume of the container must increase (this increases surface area which decreases the number of collisions per unit area which decreases the pressure). Therefore, volume and temperature are directly related at constant n and P (Charles’s law). Avogadro’s law: V % n at constant P and T CHAPTER 5 GASES 3 As gas is added to a container (n increases), there will be an immediate increase in the number of gas particle collisions with the walls of the container. This results in an increase in pressure in the container. However, the container is such that it wants to keep the pressure constant. In order to keep pressure constant, the volume of the container increases in order to reduce the collision frequency which reduces the pressure. V is directly related to n at constant P and T. Dalton’s law of partial pressure: Ptot = P1 + P2 + P3 + … The KMT assumes that gas particles are volumeless and that they exert no interparticle forces on each other. Gas molecules all behave the same way. Therefore, a mixture of gases behaves as one big gas sample. You can concentrate on the partial pressures of the individual components of the mixture or you can collectively group all of the gases together to determine the total pressure. One mole of an ideal gas behaves the same whether it is a pure gas or a mixture of gases. P vs. n relationship at constant V and T. From question 3, this is a direct relationship. As gas is added to a container, there will be an increase in the collision frequency, resulting in an increase in pressure. P and n are directly related at constant V and T. P vs. T relationship at constant V and n. From question 3, this is a direct relationship. As the temperature of the gas sample increases, the gas molecules move with a faster average velocity. This increases the gas collision frequency as well as increases the force of each gas particle collision. Both of these result in an increase in pressure. Pressure and temperature are directly related at constant V and n.
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