Chapter 5 Gases (Somewhat Unit 3 AP Chem)

Atmospheric Pressure

Pressure exerted by the weight of the gas in the atmosphere.

1 standard atmosphere (1 atm) =

760 mm Hg

760 Torr

14.69 psi

101,325 N/m² (newton/m²)

101,325 Pa (pascal)

Pgas = Patm - h

If the mercury level is higher for the end of the U-shaped tube connected to the container than the open end, then the pressure of the gas in the container is less than the atm pressure (Pgas < Patm) —— Difference

• Higher U-Shaped tube = less (Pgas) = difference

Pgas = Patm + h

If the mercury level is lower for the end of the U-shaped tube connected to the container compared to the open end, then the pressure of the gas is greater than the atm pressure (Pgas > Patm) —— Plus

• Lower U-shaped tube = greater (Pgas) = sum

Pgas = Patm

If the level of mercury is the same for the end of the U-shaped tube connected to the container compared to the open end, then Pgas = Patm

Kinetic Molecular Theory

Pressure will increase if the force of the collisions increases or if the frequency of the collisions increases. The force and the frequency of the collisions both increase with faster moving particles.

In an ideal gas at _____ it is assumed that there is ______ between gas particles, however, real gases do experience attractive forces when gas temperature is ____ and can ____ the force with which the particles collide with container walls. This caused the observed pressure of the gas to be ____ than the value predicted by the ideal gas.

Low, decrease, less

In an Ideal gas, it is assumed that the volume occupied by the gas particles themselves is zero. The free space in which the gas particles can move around is equal to the entire volume of the container. However, real gas particles do have volume, and they do occupy space in the container. This effect is noticeable when the gas pressure is very ____. When volume of the gas themselves becomes a signifcant faction of the container volume, the free space in which the gas particles particles can move around is ____. This cause the observed pressure of the real gas to be ____ than the value predicted by the ideal gas

High; Decreased; Greater

Endothermic

Process is endothermic if the system:

• Gains energy (absorbed energy)

• Energy required to break bonds is greater

• Products have more energy than reactants

• Energy flows into the system (reaction or process being studied) from surroundings

Exothermic

Process is exothermic if the system:

• Looses energy (energy is emitted or evolved)

• Energy required to break bonds is less than

• Products have less energy than reactants

• Energy flows from the system into the surroundings