Chapter 8: Solutions and Their Behavior Flashcards
What is a solution?
A homogenous mixture that consists of one or more solutes uniformly dispersed at the molecular or ionic level throughout a medium known as a solvent.
What are examples of “true solutions”?
normal saline, lactated ringers, mercury amalgam for filling tooth cavities
What is the difference between a solution and a colloid?
Colloids have larger particles in the dispersed phase, cannot be filtered, do not settle out of solution, can be stable for years, not a homogenous solution and exhibit the Tyndall effect (scattering of light passing through).
Ex of colloids: milk, blood, paint, jelly
Define solute and solvent
Solute: material that got dissolved; usually in smaller quantity
Solvent: material that does dissolving
What is the difference between saturated, unsaturated and supersaturated solutions?
saturated: maximum amount of solute per solvent at a specfic temp
unsaturated: less solute than solvent has the capacity to dissolve
supersaturated: more solute than is present in an already saturated solution, unstable - excess solute will come out of the solution crystallizing as solid, separating as liquid or bubbling out as gas
What is the molaRity of a solution?
moles of solute / liter of solution
*temperature dependent
As temp increases, molarity decreases due to volume expansion
percent w/v also temp dep
What is the molaLity of a solution?
moles of solute / kilogram of solvent
based on mass, so NOT temp dependent
percent (w/w) also based on mass so not temp dep
What is solubility?
mass of solute that will dissolve in a given amount of solvent
What factors affect solubility?
Pressure: gas solute in liquid solvent increases with increasing pressure of gas (Henry’s law), ex. pop of champagne
Pressure has little effect on liquid and solid solutes
Temperature:
solid and liquid solutes solubility increases with increasing temp
solubility of gas solutes in liquid decrease with increasing temp
How does energy flow into and out of systems?
When a solute dissolves in a solvent, there is an associated energy change. This energy change is called heat of solution or the enthalpy of solution.
It can be endothermic or exothermic.
Endothermic reaction
If tearing ions apart requires more energy than is released by solvation, then enthalpy is going to be positive (endothermic)
Energy flows from the surroundings into the system resulting in a temperature decrease in the solution
The absolute value of lattice energy (the attraction of solute particles for each other) is greater than the absolute value of the solvation energy (the attraction between solute particles and the surrounding solvent molecules)
Exothermic reaction
If the energy released by solvation is greater than the energy required to tear the ions apart, enthalpy is going to be exothermic
Energy flows out of the system (solvent and solute) into the surroundings, resulting in a temp increase in the solution
absolute value of the lattice energy is less than the absolute value of the solvation energy; dissolution of the solute causes the solution to become warmer
What are the colligative properties of solutions?
INCREASING solute concentration causes the solution:
- Vapor pressure decreases
- Boiling point increases
- Freezing point decreases
- Osmotic pressure increases
Which colligative property has the most profound impact on physical properties?
Osmotic pressure
Henry’s Law
P = Kc
P: partial pressure of the solute above the solution
K: Henry’s law constant, depends on temp
c: concentration of the solute in the solution
At a constant temperature, the amount of a given gas that dissolves in a liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid.
Solubility of gas is proportional to partial pressure of gas.
Ex. Soda is CO2 in Water
In a closed bottle: CO2 in water and above the liquid; the CO2 above the liquid presses down on the surface of liquid creating high pressure = increased gas solubility in the liquid
Open bottle: gas above liquid is released = less CO2 above liquid, less pressure pressing down = CO2 in liquid decreases in solubility = the extra CO2 that can’t be dissolved (due to dec solubility) comes out as bubbles
Henry’s law in medical setting
from her ppt:
• Increasing the partial pressure of a gas above a liquid = increases the amount of gas that dissolves in the liquid
‒ Ex: increasing the amount of anesthetic gas dialed in on the vaporizer = increases the partial pressure of the gas delivered to the patient
Graham’s Law
The rate of effusion of a gaseous substance is inversely proportional to the square root of its molar mass.
r ∝ 1/(M)^½
The ratio of the effusion rates of two gases is the square root of the inverse ratio of their molar masses
rate of effusion A / rate of effusion B = square root of (Molar mass B / Molar mass A)
her ppt:
The rate of effusion (gas diffusion through an orifice) is inversely proportional to the square root of its molecular weight
R = 1 mw
r = rate of diffusion; mw = molecular weight
Fick’s Law
Describes movement of gas across a tissue plane accounting for molecular weight, concentration gradient, solubility and membrane interactions.
Diffusion of a gas across a semipermeable membrane is directly proportional to:
- partial pressure gradient
- the membrane solubility of the gas
- membrane area
Inversely proportional to:
- membrane thickness
- molecular weight
‒ Fick’s equation describes how diffusion hypoxia occurs
• When nitrous oxide is discontinued and inspired oxygen concentration is low hypoxia can occur because the partial pressure gradient of nitrous oxide is higher than oxygen
What is diffusion?
The net movement of a molecule through space driven by the kinetic energy of the molecule.
K.E. = (1/2)mv^2
Every molecule at the same temp will have the same kinetic energy (despite its size) but its velocity may be different. Increase in temp increases kinetic energy.
Mass is inversely proportional to velocity.
Velocity is proportional to diffusion.
What is osmosis?
Osmosis is the movement of water across a semipermeable membrane to equalize the amount of solutes on each side.
Osmotic pressure: pressure needed to prevent osmosis from occurring.
Oncotic pressure: osmotic pressure exerted by plasma proteins and electrolytes in capillaries that pulls water back through the membrane
What are lipids?
Lipids are hydrophobic, nonpolar molecules that are soluble in nonpolar organic solvents.
Phospholipids have a polar head and nonpolar tail.
What is the pathway of carbohydrate metabolism? How does the liver play a role?
The liver takes glucose and stores it as glycogen.
Then it metabolizes glycogen via glycogenolysis when glucose is needed.
Surfactant therapy is used to prevent an infant’s lungs from collapsing and “sticking together.” What is a reasonable rationale for this effect?
Surfactants reduce both surface tension and adhesive forces in water.
Surfactants interrupt the attractive forces among the molecules at the surface of a liquid, resulting in less cohesion and less surface tension.
