Gas laws Flashcards
Define total pressure
the total sum of all the collision forces
Define Charles’s law
For a fixed mass of gas at a constant pressure, the volume is directly proportional to the temperature
Name the four gas laws
-Charles’s law
-Boyles’s law
-Henry’s law
-Dalton’s law
Why is Charles’s law important?
Important in lung function testing as air cools as it is expired
Define Boyle’s law
For a fixed mass of gas the product of volume and pressure are always the same providing the temperature is constant.
What’s the equation for Boyle’s law?
P x V = constant
Using Boyle’s law what happens to volume when pressure increases?
volume decreases
Equation for Boyle’s law
P1 V1 = P2 V2
Using Boyle’s law what happens when you decrease volume?
-collisions increase
-presure increases
Draw the graph fo Charles’s law
straight line
Draw the graph for Boyles law
inversly proportional curve, look at powerpoint
Define atmospheric pressure
the constant movement and collision of gas particles exerts pressure
What is pressure exerted by air known as?
barometris pressure
what is barometric pressure measured in?
kilopascals (KPa)
or
mmHg
what is barometric pressure at sea level?
101KPa
What is 1KPa equal to in mmHg?
7.5mmHg
What is 1mmHg equal to in Kpa?
0.133
Example- if the barometric pressure is 760mmHg what is the Kpa?
760 x 0.133 = 101.1 KPa
List the percentage of gases in the air
Nitrogen-78%
oxygen-20.8%
Argon-0.9%
Carbon dioxide-0.04%
other gases- 0.17%
Define Dalton’s law of partial pressure
the total pressure of a mixture of gases is equal to the sum of the partial pressure that each gas would exert in isolation.
e.g 5KPa + 15Kpa = 20 KPa
what is the equation for partial pressure?
% of gas x atmospheric pressure
example- partial pressure of oxygen- 20.9%
20.9% x 101kpa
0.209 x 101KPa
=21.1 KPa
at sea level the atmospheric pressure is 101KPa which is?
this is the sum of partial pressures of constitueant gases
What are three factors that affect the movement of gases?
-pressure gradient
-solubility of gas in liquid
-temperature
define diffusion
the movement of a substance from an area of higher concentration to an area of lower concentration
The greater the partial pressure difference between the two areas….
more rapidly the gas moves
Define Henry’s gas law
-gases dissolved in liquid
-the number of molecules dissolving in liquid is directly proportional to the partial pressure at the surface of the gas
What is the equation for Henry’s law and what does each part mean?
P = kH.C
p-partial pressure of the gas in the atmosphere above the liquid
C- concentration of dissolved gas
KH-Henry’s law constant of gas-depends on the solute, solvent and temperature
Give an example of what happens during Henry’s law
-intital state-no O2 in solution
-O2 dissolves
-at equilibrium PO2 in air and water is equal. Low O2 solubility means concerntations are not equal
What happens to pressure at high altitudes?
decreases
What happens to the partial pressure of oxygen at a high altitude?
decreases
What is the KPa of oxygen at high altitudes of 33Kpa?
20.9% x 33 = 6.90KPa
Define water vapour pressure
the pressure exerted by molecules of water vapour in gaseous form
what is the water pressure vapour standard number?
PH20= 6.3KPa at 37 degrees body temp
what is the partial pressure of moist inspired oxygen?
PIO2 =20.9% x (PB - saturated water vapour pressure at 37 degrees
pio2 = 0.209 x (101- 6.3)
=0.29 x 94.7
=19.8
what are lung volumes measurements standardised and reported at?
body temperature and pressure saturated with water (BTPS)
