Liquids and Solubility. Flashcards

Vapor pressure
Terms Definitions
How are liquids like gases?
The liquid molecules are in constant motion
How are liquids unlike gases?
Cohesive forces keep the molecules of a liquid moving near to each other
What is cohesion?
Cohesion is the attraction between like molecules. It is the responsible for the droplet formation of water.
What is adhesion?
Adhesion is the attraction between unlike molecules. It is responsible for the meniscus of water
What is the convex meniscus of mercury due to?
Greater cohesion
What is the concave meniscus of water due to
Greater adhesion
What is entropy?
It is the measure of disorder in a system
What state is entropy at its greatest?
Gases
What state is entropy at its least?
Solids
Properties of liquids (4)
Liquids take the shape of their container
Liquids are gravity dependent
Liquids unlike gases are virtually incompressible
What are Van der Waals Forces (aka London Dispersion Forces)
Occur when molecules interact strongly with each other electronically
Polar molecules with relatively positive or negative poles line up with like molecules to form a lattice like structure (H2O is an example)
Hydrogen Bonding is?
The unique characteristics of H2O molecule allows the hydrogen atoms to bond at 104 degrees angle to the oxygen atom
What does hydrogen bonds result in?
Result in a dipolar molecule with a relatively negative pole and relatively positive pole
What are necessary conditions for the formation of hydrogen bonds?
One molecule must contain a H bonded to either N, O or F and the other molecule must contain either N, O or F. If a hydrogen form between pair of molecules it will be stronger than intermolecular forces between the moleculres
What is hydrogen bonding responsible for (3)?
unexpectedly high boiling point of water
The lower density of ice compared to liquid water
The shape of many biological molecules (DNA and proteins are an example)
How is surface tension created?
Molecules of a liquid have strong cohesive forces attracting them to adjacent like molecules
Why do molecules at the surface and in middle cohere more closely than molecules on the base and the side?
They are surrounded by like molecules from all sides
What allows small insects to walk on still water?
Surface tension
What allows a needle to float on still water despite its greater density than water?
Surface tension
What is viscosity?
Is a resistance to flow due to cohesive and adhesive forces of a liquid
What does increase in temperature do to viscosity?
By weakening cohesive bonds it decreases viscosity
What is a key factor in determining flow that is laminar in nature and or through a tube?
Viscosity
What causes molecules to escape from liquid into the vapor form?
Kinetic energy
Is evaporation endothermic or exothermic?
Endothermic
What are vapors?
Molecules of a substance that have been converted to a gaseous state at temps below the substances critical temperature.
A VAPOR IS A GAS THAT CAN BE LIQUEFIED BY PRESSURE ALONE
What is critical temp?
The temp which a particular gas cannot be liquefied, no matter how much pressure is applied
What is critical temp of water?
374 Degrees Celcius
What is vapor pressure?
Vapor pressure is the pressure exerted by gas molecules in equilibrium with a liquid
When is vapor said to be saturated and what is saturation vapor pressure?
In a closed container vaporized molecules cannot escape, and a dynamic equilibrium is reached. The number of liquid and gas molecules stabilize. The vapor is said to be saturated and the pressure exerted by the vapor on the container walls is called the saturation vapor pressure.
What law does equilibrium vapor pressure illustrate?
Henrys law
What is henrys law?
At a constant temperature, the amount of a given gas dissolved in a given type and volume of liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid.
If liquid Isoflurane is ciphered into a sealed flask containing 100% oxygen calculate the partial pressures and percentages of oxygen and Isoflurane vapor in the air above the liquid?
The vapor pressure of Isoflurane is 239 mmHg and STP is 760 mmHg, therefore 760 - 239 = 521 mmHg (the pp of oxygen in the new mix of gases)
Isoflurane at 239 mmHg comprises 31.4% (239÷760) and oxygen at 521 mmHg comprises 68.6% (521÷760) of the new gas mixture.
Vapor pressures at STP of inhaled anesthetic agents
Desflurane 669 mmHg
Halothane 243 mmHg
Isoflurane 239 mmHg
Enflurane 175 mmHg
Sevoflurane 170 mmHg
Anesthetic vaporizers are "agent specific" and designed to be accurate at a specific vapor pressure. What would happen if a vaporizer was filled with the wrong anesthetic agent?
HLH and LHL
Does saturation vapor pressure (SVP) vary directly with pressure? Explain.
Yes
As heat is added, the kinetic energy level increases, more molecules escape into the vapor phase, and an increased amount of pressure is exerted on the walls of the closed container.
What gas law or laws does this illustrate ? Which variable is constant?
Gay Lussac's (The pressure of a gas of fixed mass and fixed volume is directly proportional to the gas's absolute temperature) and Henry's Laws
What is boiling point?
The boiling point is the temperature at which the vapor pressure is equal to (or begins to exceed) atmospheric pressure
When the atmospheric pressure is lowered to 733 mm Hg, will the boiling point of water be decreased or increased?
Decreased, since temperature and pressure
vary directly
What is heat of fusion?
the quantity of heat required to completely melt a substance once it has reached its melting point
What is the heat of vaporization?
the quantity of heat required to completely vaporize a substance once it has reached its boiling point.
What is humidity?
The presence of water molecules in the gaseous state in a mixture of gases
What is absolute humidity
maximum water saturation a volume of air can hold at a given temperature expressed as milligrams of water per liter of air.
What is relative humidity
actual saturation expressed as a percent of maximum possible saturation. Relative humidity ↑ as temperature ↓ because saturated vapor pressure (absolute humidity) falls
What is Dew point
temperature at which a given volume of air is cooled, excess moisture precipitates
What is humidity in the OR kept at and why
50% to reduce static electricity
What is the partial pressure of saturated water vapor at 37 degrees
47mmhg
Why are all medical gases dry?
They are dehumidified before compression
What do humidifiers do?
Add water vapor
Increase contact are and time between water and gas - "pass over , blow by, bubble diffuser, aerosol misters, jet or Venturi humidifiers"
Heat - either the water or gas to increase vaporization
Both - cascade humidifiers
What are pneumatic nebulizers?
Add liquid particles (not water vapor), and therefore are technically not humidifiers.
They use Bernoulli's principle to make aerosols
What is Bernoulli's principle
In fluid dynamics, Bernoulli's principle states that for an inviscid flow, an increase in the speed of the fluid occurs simultaneously with a decrease in pressure or a decrease in the fluid's potential energy.
What are two types of mixtures?
Mixtures are homogenous (uniform) or heterogeneous (non-uniform) in composition
How can homogenous mixtures be divided as?
into solutions & colloids based upon particle size of the solute.
What is a property of a heterogenous mixture?
Heterogeneous mixtures may have a uniform appearance, however they will separate on standing
What type of mixture is blood?
Heterogenous
What is Solubility?
The maximum amount of a substance (solute) that will dissolve in a given amount of solvent at a specific temperature
What is saturation?
A solution that contains the maximum amount of a dissolved solute at equilibrium is saturated
What coefficiant is solubility expressed as when conditions are standardized to 760 mmHg and 0 C
Bunsen coefficient
What coefficiant of solubility do physiological studes use?
Ostwald coefficient which refers to the ratio of the volume of the gas absorbed to the volume of the solvent at the temperature of the experiment (body temp).
What is solubility coefficient?
the relative affinity of a gas for two phases (ie: dissolved in blood and undissolved as a gas over the liquid) at equilibrium
What does solubility coefficient represent and what how is this significant clinically?
It represents the ratio of the volume of the solvent to the volume of the gas at equilibrium.
The Blood/Gas & Tissue/gas Solubility Coefficients of inhalation anesthetics effect their pharmacokinetics (uptake & distribution).
If a gas requires four volumes to dissolve in the blood for each one volume exerting a tension, the Blood/Gas Coefficient is
4.0
If a gas requires one volume to be dissolved in the blood for every four volumes exerting tension, it Blood/Gas Coefficient is
0.25
A very soluble gas has a higher B/G partition coefficient or lower B/G partition coefficient
higher
How is blood/gas coefficient and speed of induction related?
The LOWER the Blood/Gas Coefficient, the more RAPID is the induction.
What is oil/gas partition coefficient?
A similar relationship between the volume of a gas dissolved in a lipid tissue (oil) and that remaining in the gaseous state (exerting a pp in the plasma).
What is relationship of potency of inhaled anesthetic agent and oil/gas coefficient?
The HIGHER the Oil/Gas coefficient, the MORE POTENT the inhalation anesthetic agent.
How does pressure effect the solubility of a gas in a liquid?
The solubility of a gas overlying a liquid varies directly with pressure.
Henry's Law
Solubility of a gas in a liquid decreases as temperature increases. Why?
Solubility of a solid in a liquid increases as temperature increases. Why?
Increasing temperature increases entropy
solid e liquid e gas
What is the lambert-beer law
Relates to the concentration of a solute in solution to the intensity of a specific wavelength of light passed through the solution. It is the basis for pulse oximetry, carboximetry, infrared absorption spectroscopy (IRSAs) and capnometry
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