Chemistry Gas Laws Assignment
Chemistry Gas Laws Assignment
Chemistry Gas Laws Assignment
Gases, like other states of matter (solids , liquids and plasma), consists of
molecules or atoms . In gases, the molecules and/or atoms move freely in all
directions and bounce of the walls of the container, as it is shown on the
animation. Because every atom (or molecule) in the gas can move freely, it
means that a gas takes up all the space available to it, so that it fills the container
(unlike a liquid, or solid, that rests at the bottom of the container).
The units of pressure that are used are pascal (Pa), standard atmosphere (atm),
and torr. 1 atm is the average pressure at sea level. It is normally used as a
standard unit of pressure. The SI unit though, is the pascal. 101,325 pascals
equals 1 atm.
For laboratory work the atmosphere is very large. A more convient unit is the
torr. 760 torr equals 1 atm. A torr is the same unit as the mmHg (millimeter of
mercury). It is the pressure that is needed to raise a tube of mercury 1 millimeter.
Boyle's law or the pressure-volume law states that the volume of a given amount
of gas held at constant temperature varies inversely with the applied pressure
when the temperature and mass are constant.
PV = C
When pressure goes up, volume goes down. When volume goes up, pressure
goes down.
From the equation above, this can be derived:
This equation states that the product of the initial volume and pressure is equal
to the product of the volume and pressure after a change in one of them under
constant temperature. For example, if the initial volume was 500 mL at a pressure
of 760 torr, when the volume is compressed to 450 mL, what is the pressure?
Plug in the values:
P1V1 = P2V2
This law states that the volume of a given amount of gas held at constant
pressure is directly proportional to the Kelvin temperature.
V T
V/T=C
As the volume goes up, the temperature also goes up, and vice-versa.
Also same as before, initial and final volumes and temperatures under constant
pressure can be calculated.
V1 / T1 = V2 / T2 = V3 / T3 etc.
Gay-Lussac's Law: The Pressure Temperature Law
This law states that the pressure of a given amount of gas held at constant
volume is directly proportional to the Kelvin temperature.
P T
P/T=C
As the pressure goes up, the temperature also goes up, and vice-versa.
Also same as before, initial and final volumes and temperatures under constant
pressure can be calculated.
P1 / T1 = P2 / T2 = P3 / T3 etc.
Gives the relationship between volume and amount when pressure and
temperature are held constant. Remember amount is measured in moles. Also,
since volume is one of the variables, that means the container holding the gas is
flexible in some way and can expand or contract.
V n
This means that the volume-amount fraction will always be the same value if the
pressure and temperature remain constant.
V1 / n1 = V2 / n2 = V3 / n3 etc.
PV / T = C
As the pressure goes up, the temperature also goes up, and vice-versa.
Also same as before, initial and final volumes and temperatures under constant
pressure can be calculated.
PV = nRT
EXAMPLE 1:
The balloon used by Charles in his historic flight in 1783 was filled with
about 1300 mole of H2. If the outside temperature was 21 oC and the
atmospheric pressure was 750 mm Hg, what was the volume of the
balloon?
V ? ?
T 21 oC + 273 = 294 K