Chapter 8: Solutions and Their Behavior

Question 1

What is a solution?

Answer 1

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.

Question 2

What are examples of “true solutions”?

Answer 2

normal saline, lactated ringers, mercury amalgam for filling tooth cavities

Question 3

What is the difference between a solution and a colloid?

Answer 3

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

Question 4

Define solute and solvent

Answer 4

Solute: material that got dissolved; usually in smaller quantity

Solvent: material that does dissolving

Question 5

What is the difference between saturated, unsaturated and supersaturated solutions?

Answer 5

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

Question 6

What is the molaRity of a solution?

Answer 6

moles of solute / liter of solution

*temperature dependent
As temp increases, molarity decreases due to volume expansion
percent w/v also temp dep

Question 7

What is the molaLity of a solution?

Answer 7

moles of solute / kilogram of solvent

based on mass, so NOT temp dependent
percent (w/w) also based on mass so not temp dep

Question 8

What is solubility?

Answer 8

mass of solute that will dissolve in a given amount of solvent

Question 9

What factors affect solubility?

Answer 9

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

Question 10

How does energy flow into and out of systems?

Answer 10

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.

Question 11

Endothermic reaction

Answer 11

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)

Question 12

Exothermic reaction

Answer 12

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

Question 13

What are the colligative properties of solutions?

Answer 13

INCREASING solute concentration causes the solution:

1. Vapor pressure decreases
2. Boiling point increases
3. Freezing point decreases
4. Osmotic pressure increases

Question 14

Which colligative property has the most profound impact on physical properties?

Answer 14

Osmotic pressure

Question 15

Henry’s Law

Answer 15

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

Question 16

Henry’s law in medical setting

Answer 16

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

Question 17

Graham’s Law

Answer 17

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

Question 18

Fick’s Law

Answer 18

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

Question 19

What is diffusion?

Answer 19

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.

Question 20

What is osmosis?

Answer 20

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

Question 21

What are lipids?

Answer 21

Lipids are hydrophobic, nonpolar molecules that are soluble in nonpolar organic solvents.

Phospholipids have a polar head and nonpolar tail.

Question 22

What is the pathway of carbohydrate metabolism? How does the liver play a role?

Answer 22

The liver takes glucose and stores it as glycogen.

Then it metabolizes glycogen via glycogenolysis when glucose is needed.

Question 23

Surfactant therapy is used to prevent an infant’s lungs from collapsing and “sticking together.” What is a reasonable rationale for this effect?

Answer 23

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.