7 Solutions/Solubility, Diffusion, Tension, & Fluid Physics

Question 1

Solute

Answer 1

Solid, liquid, or gas dissolved in solvent

Solute particles must be surrounded by solvent particles

Question 2

Solvent

Answer 2

Substance into which a solute is dissolved
Dissolving agent
Body fluid solvent = water

Question 3

Solution

Answer 3

Homogenous mixture of two or more components
Particles include atoms, ions, or molecules
Solute dissolved in solvent
Ex: Sugar and water (both polar)

Question 4

Suspension

Answer 4

Solution where the solute CANNOT be dissolved in the solvent

Ex: Oil (non-polar) and water

Question 5

Colloid Solution

Answer 5

Particles exist in solution somewhere between a TRUE solution and a TRUE suspension
Size of particles - between those found in solutions and suspensions
Mixed in way that remain evenly distributed w/out settling out

Question 6

Solubility

Answer 6

Polar dissolves in polar
↑ temperature ↑ solubility
Heat (↑ temp) & energy (stirring) breaks intermolecular forces
H2O dissolves polar substances better than ethanol d/t H2O more polar (dipole-dipole & hydrogen bonding)
Solids - dissolution in solvent directly proportional to temp (100g dextrose in 100ml H2O will slightly displace volume d/t dextrose particles take up space b/w H2O molecules)
↑ temp ↑ solubility (solid in liquid)
Gases - solubility dependent on solvent nature and temp
↑ temp ↓ solubility (gas in liquid)
Endothermic & exothermic reactions

Question 7

Solution Strength CALCULATION

Answer 7

Solute grams per 100mL solvent = % solution
Percent = per 100
0.9% NaCl = 0.9g NaCl / 100mL
Molar solution - solute moles per 1L solvent
NaCl = 23 + 35AMU = 58g/mol
0.9g NaCl / 100mL = 9g / 1L
(9g/L) / (58g/mol) = 0.155 moles

Question 8

Henry’s Law

Answer 8

Amount gas dissolved in liquid directly proportional to the pressure applied to the gas as it overlies the liquid
Temperature also affects gas solubility (inversely proportional)
40mmHg pressure applied therefore 40mmHg pressure from gas molecules w/in the solution

Question 9

Diffusion

Answer 9

Process by which substance spreads through the space available to it by random molecular motion
Molecules more from area of high to low concentration
Pressure gradient ∆P
P1 - P2 > 0

Question 10

Graham’s Law

Answer 10

Describes gas movement from one compartment to another through a porous membrane (diffusion) or small opening such as an orifice (effusion)
Diffusion α 1/√Molecular Weight
Directly proportional to solubility
Larger, more cumbersome molecules = less diffusion

Question 11

Graham’s Law CALCULATION

Answer 11

Diffusion coefficient = Gas solubility / √Molecular weight
= Gas 1 Diffusion Rate / Gas 2 Diffusion Rate
= (Gas 1 Solubility / Gas 2 Solubility) x (√Gas 2 MW /√Gas 1 MW)
Given solubility - Gas A 20x more soluble than Gas B
Relative rate of diffusion

Question 12

Fick’s Law

Answer 12

Describes gas volume that diffuses across membrane per minute
Diffusion rate = (Area x Diffusion coefficient x ∆P) / Membrane thickness
r/t alveolar capillary membrane
↑ surface area ↑ diffusion
↑ thickness ↓ diffusion

Question 13

Turbulent Flow

Answer 13

Density more important
Influences probability that interactions b/w fluid molecules will occur
↑ density = ↑ molecules per unit area therefore ↑ change molecular collisions ↑ drag (resistance) ↓ flow

Question 14

Gas Diffusion/Effusion

Answer 14

Diffusion - porous membrane; gradual gas mixing d/t motion of component particles
Effusion - escape of gaseous molecules via small opening (orifice) into evacuated space
α 1/√MW
α 1/√Density
Less dense gas ↑ diffusion/effusion

Question 15

Bunsen Solubility Coefficient α

Answer 15

Gas volume in liquid unit at 0°C and 760mmHg
Expressed as numerical value for particular gas in given liquid
= mL gas per 1 mL H2O

Question 16

Ostwald Solubility Coefficient λ

Answer 16

Defined as ratio of gas volume absorbed to the solvent volume at body temp 37°C and ambient pressure
Used to express the blood/gas and tissue/gas ratio
“Blood-gas partition coefficient”

Question 17

Law of Laplace

Answer 17

Defines the pressure gradient across the wall of sphere (alveoli) or cylinder (blood vessels and airway) which are r/t surface tension and radius

Question 18

Laplace CALCULATIONS

Answer 18

Tension defined as internal force generated by structure
Sphere
T = (P x r) / 2
Cylinder
T = P x r
Pressure inversely proportional to the radius
P α 1 / r
Small vs. large alveoli pressure gradient w/out surfactant

Question 19

Surfactant

Answer 19

Amphipathic detergent
Produced by Type II alveolar cells
Equalizes pressures w/in small and large alveoli
Surfactant present in alveoli to ↓ surface tension d/t ALI
Increased efficacy in smaller radius alveoli (well-organized structure/orientation)

Question 20

Surface Tension

Answer 20

Created at the interface (ALI) b/w liquid and gas where liquid molecules are pulled together by intermolecular (cohesive) forces
Air non-polar and H2O polar
Pel 2/3 surface tension and 1/3 elastic intrinsic factors (type, number, health of fibers)
Know relationship to surfactant

Question 21

Micelle

Answer 21

Aggregate of surfactant molecules dispersed in liquid forming a colloidal suspension
Hydrophilic (polar) head in contact w/ solvent and hydrophobic (non-polar) tail w/in micelle center

Question 22

Poiseuille’s Law

Answer 22

Laminar flow
F = (π ⋅ r^4 ⋅ ∆P) / (8 ⋅ η ⋅ L)
F = ∆P / R
Directly proportional to ∆P and r^4
Inversely proportional to viscosity and length
Resistance opposite (inverse to r^4 and direct to viscosity and length)
R α 1 / r^4
↓ viscosity ↑ flow
Application: 18G vs. 24G (diameter), increased hydrostatic pressure (∆P), polycythemia/anemia (viscosity) impact on flow

Question 23

Reynolds Number

Answer 23

Predicts when flow through tube changes from laminar to turbulent
(Inertial Forces)/(Cohesive Forces)
< 2,000 Laminar Flow
2,000-4,000 Transitional
> 4,000 Turbulent Flow
Re = (velocity ⋅ diameter ⋅ density)/viscosity
Does not consider or predict resistance

Question 24

Laminar → Turbulent Flow

Answer 24

Reynolds number > 4,000
High flow of velocity
Tube narrows or kink/bend/angle
Roughness on tube wall (mucus, clot, etc.)
Fluid flows through an orifice
Resistance to flow increases when turbulent
Density determines turbulent flow (not viscosity)