Mod 17: Gas Laws

What is the formula for Universal Gas Law?

PV = nRT

Do you need to know the universal gas law for the exam?

YES!

What does universal gas law describe?

behavior of gases and vapors with certain variables

What are the variables of universal gas law?

• P = pressure (atm)

• n = number of moles of substance

• R = universal gas constant (0.08)(requires pressure in atm)

• V = volume taken up by mass of gas (L)

• T = temperature (K) MUST BE IN KELVIN

What unit must pressure be measured in (universal gas law)?

atmospheres

What unit must temperature be measured in (universal gas law)?

kelvin

Why is temp measure in kelvin (universal gas law)?

because it has no negative numbers

What unit is volume measured in (universal gas law)?

liters

What value is the universal constant?

0.08

What are moles?

a gram molecular weight of a gas

What is molecular/atomic weight?

the sum of all atomic particles (electrons, protons, and neutrons) in atom/molecule

What is an example of an atom’s moles?

helium has an atomic weight of 4

• 4 grams = one mole of helium

What is Avogadro’s number?

6.023 × 10²³ units

What is Avogadro’s Hypothesis?

one mole of any gas at 0C (273 K) and 1 atm (standard pressure), will expand to 22.4 liters

• PV =nrT

What happens when variables in UGL is manipulated?

changes in other variables will occur

What are gas laws mathematical expressions of?

how Boyle’s law, charles, and gay lussac’s law are related

Which each of the 3 laws, …

one variable is held constant.

memorize this

What is constant in Boyle’s Law?

temp

In Boyle’s Law, what is inversely proportional?

pressure and temp

nr can also be known as …

k

When solving gas law equations, what it is important to know?

you want the variables (components that are changing) on the same side of the equation together

For boyle’s law how would you write the equation?

Tk = PV

the things changing are on the same side

What is a clinical application of Boyle’s Law?

breathing in and out

What is constant in Charle’s law?

pressure

what is directly proportional in charle’s law?

volume and temp

What is the constant in Gay-Lussac’s Law?

volume

What is directly proportional in Gay-Lussac’s Law?

pressure and temp

What can also call the UGL and why?

the ideal gas law; explains gases behavior if they were ideal

What factors does the UGL omit?

1. a gas molecule’s small volume

2. intermolecular interactions

Why was kinetic molecular theory created?

to encompass charles, boyle, and gay-lussac AND laws of motion AND thermodynamics

KMT was created because UGL was …

omitting factors

What does an ideal gas also assume?

no intermolecular forces

What 3 things does Van der Waal’s equation do?

1. corrects the UGL

2. accounts for molecular volume

3. accounts for molecular interaction in a gas

What is pressure in KMT the result of?

molecular collisions on the walls of a container

More molecules in a container =

more collisions = increased pressure

What does Dalton’s Law state?

the total pressure of a system is the additive pressures of each individual gas in a mixture

What will multiple gases in a mixture exert?

a pressure in proportion to its percentage in the mixture

In Dalton’s Law, what is the total pressure?

the sum of all molecular collisions upon the walls of a container

Pt = p1 + p2 + p3 + p4

When are partial pressures equal?

at equilibrium

What does MAC stand for?

mean alveolar concentration

What is MAC?

the minimum alveolar concentration (at 1 atm) at which 50% of patients will not respond/move to noxious stimuli

What is 1 mac of sevoflurane?

2%

What is 1 mac of isoflurane?

1.2%

What is 1 mac of desflurane?

6%

true or false. MAC cannot be used in multiple calculations.

false

What is a vapor?

a substance in its gaseous state, but currently below critical temp

What is a gas?

a substance above its critical temp

What happens to vapor pressure as temp increases?

it increases

liquids with high intermolecular forces have what kind of vapor pressure?

low (h2o)

liquids with low intermolecular forces have what kind of vapor pressure?

high (desflurane)

When does a liquid boil?

when its VP = atmospheric pressure above the liquid

Do boiling points vary with atmospheric pressure?

yes

What happens if a volatile agent with a higher

vapor pressure is added to a vaporizer calibrated

for a lower vapor pressure? The concentration

delivered will be…

higher than normal, Higher Lower Higher

What happens if a volatile agent with a lower

vapor pressure is added to a vaporizer calibrated

for a higher vapor pressure? The concentration

delivered will be…..

lower than normal, Lower Higher Low

What is VP dependent on? (not temp)

solubility of the substance

What is a coefficient?

a constant number that measures a specific material property or how a substance reacts under certain conditions

What is solubility coefficient?

a number that tells you how much of a gas can dissolve in a liquid at a certain pressure and temperature

In is solubility coefficient at equilibrium?

when the partial pressure of gas in vapor state is equal to that in liquid state - no gradient exists to push in either direction

What is a partition coefficient?

number that tell us how a chemical substance splits itself between two mixed, unmixable liquids

what is a blood:gas partition coefficient?

a measure of how an anesthetic gas dissolves in blood compared to the air in the lungs

What is the Ostwald Solubility Coffecient?

a measure of how well a gas dissolves in a liquid at a 37C (body temp)

What is the bood:gas partition coefficient for sevoflurane?

0.65

What is the blood:gas coefficient for isoflurane?

1.46

What is the blood:gas coefficient for desflurane?

0.42

What is the adiabatic process?

rapid expansion or compression of gases that occurs faster than energy can equilibrate with the surrounding environment

true or false. adiabatic process can increase or decrease the energy in the system.

false, it do neither

What is the energy concentration effect?

• rapid compression of gas cause ⬆kinetic energy, which ⬆temp when it occurs faster than the energy can equilibrate with the environment

• temp will increase proportionally to the decreased volume

• oil or grease not recommended for use on cylinder of compressed gas → risk of ignition or burn

What is the energy dilution, joule-thompson effect?

• explains the cooling effect that occurs with rapid gas expansion (opposite of rapid compression)

• “joule is cool”

• frosting may occur

• how a cryoprobe works

How does the energy dilution, joule thomson effect actually happen?

rapid pressure decrease of a gas, lowers the energy per area, which lowers the temperature