Flashcards in Gas Laws Deck (47):
What is meant by standard molar volume?
At STP (1 atm and 0C), 1 mole of ideal gas has a volume of 22.4L or 22.7L (dependning on the text)
What are the 4 quantities that describe the state of a gas?
- number of moles
What is Boyle’s law?
When temperature is constant—> volume and pressure are inversely related
What is Charle’s law?
V1/T1 = V2/T2
If pressure is constant—> gas expands (volume increases) when heated (directly proportionate)
* also called the law of volume
What is Avogadro’s number?
6.022 x 10^23
What does Avogadro say?
V1/N1 = V2/N2
At equal temperature and pressure, equal volumes of gas contain equal number of particles (molecules)
How to you calculate kelvin?
Celcius + 273.15
What is Gay-Lusac’s Law?
P1/T1 = P2/T2
If volume is constant—> pressure is directly proportional to temperature
What is the ideal gas law?
*describes the behavior of an ideal gas under all conditions *
n= number of moles
R= constant (0.08205)
T= temperature (K)
T/F: Unlike solids or liquids, gas density depends strongly on temperature and pressure?
What is Dalton’s law of partial pressures?
The total pressure of a mixture of gases is equal to the sum of the partial pressure of the component gases.
Ptotal= P1 + P2 + P3.....
1 atm= 0.79atm + 0.21 atm
What are the partial pressures of inhaled anesthetic gases?
Sevo: 157 mmHg
Iso: 240 mmHg
What is mole fraction?
A way of expressing the relative proportion of 1 particular gas within a mixture of gases.
Xa= mol A/(mol A + mol B + mol C)
What does relative humidity measure?
The saturation of water in the air
RH= (mass of water in air)/(mass of water that will fit in air)
Warmer air will hold more water. What does this mean as the air cools?
As it cools humidity increases. As water concentration exceeds the solubility of water dew will form—> dew point
Maximum solubility of water in the air is directly related to ________________.
Vapor pressure of water
What is the relative humidity in a closed container?
What happens to relative humidity as temperature goes down?
Relative humidity increases
What is the vapor pressure of water at body temp (37C)?
What is stated in the Kinetic Theory of Gases?
- gases consist of small particles, where volume is negligible compared to the volume of the gas
- gas molecules are in constant, random motion
- no attractive or repulsive forces exist between gas particle—> collisions are elastic
- average kinetic energy depends only on temperature (and is a distribution)
How do you find the density of a gas?
Sum of mass of molecules/ volume gas occupies
What is the equation for the pressure of a gas?
Pressure = Force/area
What does temperature of a gas really measure?
Mean kinetic energy of gas
- the higher the temperature, the greater the motion
- temperature is directly proportional to average kinetic energy
How do you find the internal energy?
kinetic energy + potential
Does average kinetic energy depend of the identity of the gas?
No, average kinetic energy depends on temperature
Define effusion and diffusion?
Effusion= movement of gas through a small opening
Diffusion= movement from high to low concentration
*effusion and diffusion are substantially the same process *
What is Graham’s Law of Effusion?
The rate of effusion is inversely proportional to the square root of the molecular mass, and depends on speed of molecules
Rate A/ Rate B = the square root of (mmB/mmA)
Mm= molecular mass
* The premise is that heavier gas molecules will move more slowly
What is Fick’s law?
Rate = D x A x P1-P2/ (T x square root of molecular weight)
D= diffusion coefficient
A= surface area
P1-P2= difference of partial pressure of gas across membrane
T= thickness of membrane
Said another way, the rate of diffusion across a membrane is determined by:
- chemical nature of the membrane itself (diffusion coefficient)
- surface area of membrane
- partial pressure gradient of the gas across the membrane
- thickness of membrane
What is a real life application of Fick’s law?
Applies to gas in alveoli going into tissues
What are diffusion and perfusion-limited gas exchange distinguished by?
The extent that an alveolar gas’s partial pressure will equilibrium across the alveolar membrane as blood flows through the pulmonary capillaries
Since nitrous oxide has such a rapid diffusion rate, and consequently rapid partial pressure equillibration, what is the principle factor limiting transport of nitrous oxide away from the lungs?
The rate of blood flow through pulmonary capillaries—> “perfusion limitation”
What main points does Fick’s law explain?
- the concentration effect
- the 2nd gas effect
- diffusion hypoxia
- why nitrous leads to increase in volume and increase in pressure in gas spaces in the body
CO2 is larger than O2. Why does it diffuse faster across alveolar and capillary membranes?
CO2 is 20 times more soluble
How does a fetus receive O2 and drugs?
Simple diffusion across a membrane
Diffusion requires ________________.
A difference in partial pressures
What does Henry’s law state?
The amount of a non-reactive gas which dissolves in liquid is directly proportionate to the partial pressure of gas (if temperature remains constant)
- permits calculation of dissolved CO2 and O2 in blood
How much O2 is dissolved in blood, and how do you calculate it if you know the partial pressure?
Dissolved O2 in blood is 0.003mL/100mL blood/mmHg partial pressure of O2
—> multiple pp of O2 by 0.003
How does Henry’s law relate to temperature?
The amount of gas dissolved is inversely proportionate to temperature—> the colder the liquid,the more gas that will dissolve
- in the O.R. The colder your patient is—> gas will hang around longer
What is Ostwald’s solubility coefficient?
(Aka the blood:gas partition coefficient)
The ratio of concentration of a compound in 1 solvent to the concentration in another solvent at equilibrium
- describes how gas will partition itself between the 2 phases after equilibrium is reached
The higher the coefficient, the more readily the gas dissolves in the liquid
Enflurane has a blood:gas partition coefficient of 1.8. What does this mean?
1.8 times the concentration in the blood than in the alveoli
A higher partition coefficient means:
Higher lipophillicity= higher potency = higher solubility
What does higher solubility in blood mean?
More agent needs to be dissolved—> slower onset
MAC decreases as blood gas partition coefficient increases, usually
What is stated by Meyer-Overton?
Agents with increased oil solubility have greater potency, due to the cell’s lipid membrane
* later disproved—> experiments proved protein, ion changes or enzymes were the cause (inhibition of Luciferase enzyme)
What are the differences between ideal and real gasses?
Ideal: obey laws at all temperatures and pressures * there are no ideal gases *
Real: deviate at high pressure and/or temperatures
- van der waals equation deals with this deviation
What is understood under the van der waals relationship?
- Assumes gas molecules have finite volumes
- and gas molecules attract one another (van der waals forces)
* these forces must be broken for liquid molecules to enter gas phase *
What is the Joule-Thompson effect?
- as a cylinder of compressed gas empties, the cylinder cools
—> this is how a cryoprobe works