Chemistry Physics Notes
7/7 & 14

Symbols P=pressure V=volume T= temp

STD= standard temp and pressure, which means 0 K & 760mmHg – occurs at sea level. As increase distance from sea level -> chg in PaP occur, therefore anesthesia is delivered differently depending on the Atm pr. They will give us a formula for this later.

PaP = partial pressure

Metric –
weight- gm, mg mcg
Volume- liter, ml
Length – meter

T – is a way of measuring the average kinetic energy of the molecules in a substance, or the average kinetic velocity of molecules, it is work or movt.

Potential energy is stored energy which is ready to produce work

Scales of temp F, C, K

C=5/9(F-32) F=9/5(c)+32 K=C+273

Matter – can be broken down into elements building blocks

• occupies space and has mass
• not created or destroyed
• exists in 3 states –
  • solid- definite shape
  • liquid- definite volume, variable shape
  • gas- no definite shape or volume

Elemental building blocks – atoms

Atomic # - A# - corresponds to # of protons in nuc

Atomic wt-AW- mass of atom in terms of the weight of the neutrons and protons in grams. E’s weight not counted because of bonding and their too light anyway

Oxygen’s A#=8 (protons) AW=16(protons & neutrons)

Avagadro’s # - 6.02 X 10 23^rd molecules are present , but the A# & AW will vary because the weight of each different atom varies

Conversion – 1ATM = 760mmHg = 14.07PSI

1 mmHg = 1.36 or 1.4 Cm H2O

Bohr Model – looks at reactivity,

- Theory of octets

- Valence (outer most shell) strives for stability by trying to achieve

noble gas configuration

• the more stable, the less reactive
• gp 1A is the most reactive
• gp 5,6,7 are moderately reactive
• gp 8 not reactive because the octet exists, therefore electrons doesn't have to leave or bond.

Li – One e donated so configuration goes to He -> Li+

K donates one e so the configuration goes to Ar, -> K+

C has 4 valence e’s so depending on what C reacts with determines whether e’s are donated or accepted (kind of bond)

N-5VE O- 6VE F – 7VE

Bonding

• ionic – when e’s from one shell leaves and goes to another atom

Na – 1 e -> Na+

• Covalent – e’s shared between 2 atoms

Polar – molecule has a + and – end, and e hangs more toward one

end of the molecule than the other. The distance from

electron to nucleus in not equidistant

Non Polar – e’s are equidistant between nuclei because there are

no neg – or+ forces pulling e to one side or the other

Univalent bonding- + valence # means atom donates e, and the

accepting atom is called a negative valence

Na+ Cl- refer to the valence of the atom

Isotopes are elements with different AW

Like C12 & C14. Isotopes react with elements with some differences

Cohesion – RT kinetic nrg and state of matter

• solids possess the most cohesion
• add nrg and molecules move more-> dec cohesion
• gasses have no or dec cohesive forces
• cohesive forces dim as molecules move apart

Adhesion – similar concept but the molec are not alike?

Gas laws abbr IG=ideal gas

RG=real gas

PV=nRT – formula

P=pressure, V=volume, n=#moles, R=gas constant, T=temp

B=Boyles law

C=Charles

G=Gay-Lussacs

D=Daltons

G=Grahams

L=LaPlaces

Gas laws work for ideal gasses only, and is theoretical. The molecules considered are far apart and have no attraction

Rare gasses exist only in the lab and have negligible cohesiveness

They behave like Ig(ne, AR) when for eg (inc T & dec P)

P = The force exerted on a cylinder side wall

Collisions occur inside the cylinder

The inc P causes inc collisions

Dec P causes dec collisions

Pressure is measured by means of measuring a column of liquid (Hg or

H2O) in which the level of the column of liquid is maintained

In reducing the V of a gas (compressing it) means P is inc but T remains constant

All gas laws are different variations of the IG laws

Grahams Law-

- diffusion rate = 1/ mw sq root of mw, don’t forget radical sign

- when gasses are liberated, they dispense quickly in order to fill the space

that are occupying, think of trying to achieve = pressures in both areas

picture

• applies to anesthesia gasses
• rate of diffusion of a gas compared to another gas varies inversely with the sq root of the mw( reciprocal) of time with uptake - can plot out uptake of anesthesia gas for eg 1 large molecule diffuses slower than a small molecule, but the solubility of a molecule can alter this rule.
• Not considering solubility - H+ diffuses quicker than F
• Consider solubility - CO2 diffuses 20 times faster than O2, because its more soluble than O2, even though its larger than O2

Daltons law - the total pressure exerted is = to the pressure of all the gasses in the mixture.

• eg RA is 21% O2 , to get the PaO2 multiply .21 x 760 = 660 which tells us how much Pa P is exerted for each gas.

If vapor pressure - (VP) of isoforane is 239, then figure its PaP when mixed in 100% O2. 100% = 1.0 x 760 = 760 - (239) = 521 = 68.5% O2 is mixed with isoforane

VPT - can stay constant - we are looking at the % of what gas exerts what pressure in a container. Then add the sums of all the pressures that are exerted

VP is the pressure necessary to keep the mixture in liquid state( liquid readily wants to go the gasseous state

Gas changes - Triangle G C=T&V at const P

T P G=T&P at const V

C V B B=V&P at const T

B - at constant T, P&V vary inversely - P1V!=P2V2

Eg 400mg x 8L = 1600 mg x y, y = 2L, notice the proportionality of the #'s

• squeeze ambu and - inc pr with in bag and volume of gas out of bag which changes pr in pt( inc pr in pt)
• spontaneous resps - neg pr leads to inspired  vol of gas

C - T&V at constant P, V directly prop to T in Kelvin at const P

• LMA cuff expands during steam sterilization, if it isn't deflated.
• V1(6L) = V2(36L)

T1( 9) T2 (x) T2 = 54

G - P directly prop to T is V is constant, PV = nRT, as gas is released form a cylinder of compressed gas, then pressure inside will gradually dec and will be indicated on gauge ( think of moles of gas being released)

Bourdon gauge - measures hi pressure in cylinder

• relative to atmospheric pr
• therefore absolute pressure is not measured
• even though gauge says zero there may still be gas in the tank

LaPlaces law - tension may be defined a sthe internal force generated by a structure - for Cylinders - T = Pr where P- pr of fld in cyl, r- radius, T-tension

blood vs - the tension in the wall is proportional to the

radius, therefore the larger the radius, the

higher the tension , and the > likely the vs is to

rupture

heart - > filling pressure = > tension in the ventricular

wall, which is related to Starling & preload

Spheres - T = (Pr) / 2

Alveoli - with surfactant open and round,

collapsed with out surfactant -

Critical Temp is associated with compressed gasses

- gasses will liquefy if sufficient pr is applied and T is below the critical

value.

• if gas is above CT, it can not be liquefied even by altering pressure
• so at room temp a compressed cylinder of liq 02 wont stay liquid because the critical temp is -119C, therefore O2 cylinders are compressed gas
• N2O CT is 39.5C so it can be stored in a cylinder as a liquid, but the gauge will read 400 until all of the liquid is gone, because the liquid exerts the pressure even despite how much the volume of it is reduced

Joule-Thompson effect-

• explains why cylinders cool when opened and gas is escaping, open valve and condensation on valve is seen, because it takes up energy as it comes out??????
• If valve is not cooled, heating up can occur = explosion (opening hosp pipes of gas causes adietic heat concentration
• Release of gas into dead space can heat a small orifice, so be sure to let gas out slowly
• Open into a closed space and heating occurs in the pipe = explosion
• Open into an open space and cooling occurs

Avagadro's Law - one mol of any gas at some temp has the same # of molecules( but probably wont weigh the same)

• 1 mol of any gas at STP fills 22.4 L
• = vols of gas under the same P&T, contain the same # of molecules
• if there is I mol of N at 760mmHg & const T = 1 mol O2 at 760 & con T
• diffusion is affected and different per different gas (bec of the wt), think of the rate of flow of the same amt of molecules of different gasses and how gasses are delivered

Gram Molecular Weight- is the weight of 1 mol of a substance

• expressed in gms
• it is what one mol weighs - 1 mol O2 is 32gms

Diffusion - VanDer Waals forces

• are mutual attraction brought about by electrical charges of a gas
• need to overcome VDW forces in order to separate the molecules
• think of cohesion

Ficks Law of Diffusion - a gas always diffuses from an area of > pr to area of

< pr

• rate of diffusion thru a membrane means there is a difference in

pressure

rate of diffusion = P1-P2(area)(soluability) / (memb thickness) (sq rt mw)

the diff rate is directly proportional to the Pa P gradient, the area of the membrane its passing thru, and the soluability of the gas that is diffusing thru the membrane

• DR is inversly proportional to the Membr thickness and Sq rt MW
• CO2&O2 in lungs

• density of local anes / density of CSF
• SG of CSF is 1.001 - 1.005 at 37C
• 3 types of baricity

where you put it

2. hypotonic - lighter than CSF so it will go up

3. hyperbaric - heavier than CSF so it will go down

1,2 are usually used

Density = M / V Gas Density = GM wt / GM vol

GMV = Molec wt of the gas / wt of gas per liter

 

Know Vapor

1. gas goes through vaporizer
2. picks up anes gasses
3. how this affect changing dial
4. quickest way to get anesthesia gasses to pt
5. inc flow thru so deliver more flow thru
6. dial gives what % delivery of what gas
7. know vapor pressure, 100% O2,
8. del anes in denver is different than here - why?
9. Understand the theory of gas laws
10. Know concepts of why inhalants work
11. Bernoulis iffect
12. Inc IV guage from 22-18 change diameter and inc vol bu 4 in the same amt of time

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