Chem Exam 2

Question 1

Solution

Answer 1

Homogenous mixture that consists of one or more solutes uniformly dispersed at molecular or ionic level throughout a medium known as the solvent

• Not always liquid
  Ex: Air: solution of nitrogen, oxygen, other gases
  Former dental fillings: silver amalgams (mix of silver and mercury)

Question 2

Homogenous mixture

Answer 2

Not possible to discern boundaries between components of the mixture. Ex: Normal saline (uniform throughout sample)

Question 3

Phase Boundary

Answer 3

Separates regions of a mixture where the chemical or physical properties of the mixture change

Question 4

Solute

Answer 4

Material that got dissolved; component kf solution present in smaller quantity. Ex: Sodium chloride

Question 5

Solvent

Answer 5

Material that does dissolving, usually water

Question 6

Molarity (molar concentration)

Answer 6

Moles of solute per liter of solution
M = mol of solute/L of solution (mol/L)

• Molar concentrations are conversion factors btw moles of material and liters of solution
• Depends on temperature of solution
  Molar concentration will decrease at temperature increases

Question 7

Molality (molal concentration)

Answer 7

Express concentration in terms of moles of solute per kilogram of solvent
m=mol of solute/kg of solute

• Used in physical chemistry -> quantities of solute and solvent are considered separately
• Mass is not temperature dependent, molality is not temperature dependent
• Less convenient in analysis bc quantities of a solution measured out by volume or mass in lab include both solute and solvent
• When doing stoichiometry, molality requires additional calculation to take into

Question 8

Molarity vs Molality

Answer 8

Molality and molarity are never equal, but difference is is smaller as solutions become more dilute

Convert btw molarity and molality, need to know density of solution

molality of solution = x mol of solute/y kg of solvent

Question 9

Percent by weight to volume

%w/v

Answer 9

The percent of concentration you encounter in a clinical setting when measuring out a volume of medicine in syringe

Grams of solute per 100mL of solution

%w/v = g of solute/100mL of solution
OR
%w/v= g of solute/mL of solution (100%)

First equation is useful as a conversion factor btw grams of solute and milliliters of solution

Second equation is useful tp calculate concentration of a solution

• To relate to percent by weight to percent weight to volume, use the density of solution

Percent by volume (%v/v): never used in analytical lab bc values are not additive

Question 10

Equivalents (Eq)

Answer 10

Analogous to a mole

Question 11

Normality

Answer 11

Analogous to molarity

Question 12

Normality and equivalents

Answer 12

1 equivalent of a substance contains 1 mole of chemical reactivity

N= equivalents of solute/L of solution

Normality is equal to equivalents of solute per liter of solution

Unless context of chemistry is specified, normality is ambiguous

Question 13

Parts per million

Answer 13

Concentration of extremely dilute solutions is sometimes expressed as part per million

A ppm concentration is analogous to a percent concentration, except you are comparing amount of solute to a million grams of solute instead of 100 gram.

ppm = g of solute/1x10^6g of solution =

g of solute/g of solution (1x10^6)ppm

Question 14

Solubility

Answer 14

Some solutes are more soluble in given solute than others

The solubility of solute is amount of solute that will dissolve in a given amount of solvent at a given temp

Saturated solution contains maximum amount of a solute, as defined by its solubility. No more solute will dissolve in a solution saturated with solute. if solution is not saturated, more solute will dissolve in solution.

Question 15

Supersaturated solution

Answer 15

Supersaturated solution contains more solute than allowed by solubility of solute.

• NOT a stable system, bc there is more solute dissolved in sample than solvent can accommodate
• Excess solute will come out of solution, crystallizing as a solid, separating as a liquid, or bubbling out as a gas
  Ex: when blood or urine in kidneys become supersaturated with calcium oxalate or calcium phos, kidney stone can form
• If solute is a gas in liquid solvent, will see bubbles forming in solution (Fizz when opening bottle of beer or soda)

Question 16

Miscibility

Answer 16

Two liquids are miscible if they are soluble I each other in all proportions

Ex: Alcohol and water are miscible with each other.
Oil and water are immiscible

Like dissolves like

• Polar solutes are more soluble in polar solvents
• Nonpolar solutes are more soluble in non polar solvents; insoluble in water
• Most organic molecules are nonpolar
• Most ionic compounds are polar -> dissolve in water but not soluble in organic compounds (ether, hexane)

Question 17

Energy Changes

Answer 17

When a solute dissolves in a solvent, there is an associated energy change and temperature change to solution

The energy change when using heat and cold packs is called heat of solution or the enthalpy of solution:

Δhsoln

Defined as the energy change that accompanies dissolving exactly 1 mole of solute in a given solvent

Enthalpy H is equal to the heat Q as long as the pressure remains constant

The energy change may be endothermic or exothermic

Whether the heat of solution is endothermic or exothermic depends on the relative magnitudes of the lattice energy and the heat of solvation
* If tearing the ions apart requires more energy than is released by solvation, then “Δ”Hsoln is going to be positive (endothermic)

• If the energy released by solvation is greater than the energy required to tear the ions apart, “Δ”Hsoln is going to be exothermic

Question 18

Exothermic

Answer 18

• If the solution process is exothermic, energy flows out of the system (solvent and solute) into the surroundings, resulting in a temperature increase in the solution
• Energy is lost

Question 19

Endothermic

Answer 19

• If the solution process is endothermic, energy flows from the surroundings into the system, resulting in a temperature decrease in the solution
• Energy is gained

Question 20

Effect of Pressure on Solubility

Answer 20

As pressure increases, the solubility of a gaseous solute in a liquid solvent increases
* With less pressure, solubility of gaseous solute decreases (CO2 escaping champagne bottle)

• Since solids and liquids are not very compressible, at least not compared to gases, pressure has very little effect on the solubility of solid and liquid solutes

The quantitative relationship between pressure and solubility is given by Henry’s law:

S = k(H)P(gas)

S = solubility
kH = Henry’s law constant (0.042g/L/atm
Pgas = partial pressure of the gas

Increased partial pressure of gas -> more gaseous molecules zipping around at near surface of the liquid

Question 21

Effect of Temperature on Solubility

Answer 21

The solubility of solid and liquid solutes in liquid solvents generally increases with increasing temperature

• As temperature increases, vapor pressure of gaseous solutes increases to point that they escape the solvent into gas phase

Question 22

Colligative Properties

Vapor Pressure

Answer 22

The vapor pressure of a solution Decreases with increasing solute concentration

The vapor pressure of a liquid results from the most energetic molecules near the surface of the liquid escaping into the gas phase

The most likely escape sites for the liquid molecules are at or near the surface of the liquid

As we begin to introduce solute molecules, some of these escape sites are occupied by the solute molecules, so fewer solvent molecules can escape into the gas phase

Therefore, the vapor pressure of the solution is less than the vapor pressure of the pure solvent

Raoult’s law states the vapor pressure of a volatile component of a solution (P) is equal to the vapor pressure of the pure substance (Po) times the mole fraction (ᵡ) of that substance

P = χPo

Question 23

Colligative Properties

Boiling Point

Answer 23

The boiling point of a solution INCREASES with increasing solute concentration

Temperature at which the vapor pressure of the material is equal to the ambient pressure

The boiling point of a solution increases as the concentration of solute(s) increases

The change in boiling point is directly proportional to the molal concentration of the solute particles

ΔTbp = Tbp,solution – Tbp,solvent = kbp · mtotal

ΔTbp = the number of degrees by which the boiling point increases
Tbp,solution = the boiling point of the solution, Tbp,solvent = the boiling point of the pure solvent
kbp = a constant (called the ebullioscopic constant) that is characteristic of the solvent
mtotal = the molal concentration of all solute particles

Activity is the effective concentration of a solute
Activity is always less than molality

Question 24

Colligative Properties

Freezing Point

Answer 24

The freezing point of a solution DECREASES with increasing solute concentration

Temperature at which the liquid phase of the material is in equilibrium with the solid phase

In order to enter into the solid state, the molecules (or ions or atoms) of the sample need to settle into an orderly, crystalline lattice structure

The presence of solute particles interferes with this process by getting in the way

It is necessary to cool the sample to lower temperatures, thereby lowering the kinetic energy of the molecules even further, before they will settle into the solid phase

The relationship that quantifies the degrees of freezing point depression has an identical form to boiling point elevation

ΔTfp = Tfp,solution − Tfp,solvent = kfp · mtotal

ΔTfp = the number of degrees by which the freezing point decreases
Tfp,solution = the  freezing point of the solution, Tfp,solvent = the freezing point of the pure solvent
kfp = a constant (called the cryoscopic constant) that is characteristic of the solvent
mtotal = the molal concentration of all solute particles

Question 25

Colligative Properties

Osmotic Pressure

Answer 25

The osmotic pressure of a solution INCREASES with increasing solute concentration

Osmosis is diffusion of water through a semipermeable membrane

The relative concentration of solutes in osmotic systems is called the tonicity

Two solutions are isotonic if they contain equal concentrations of particles

Hypertonic: higher concentration of solute

Hypotonic: lower concentration of solute

Osmosis always spontaneously occurs from the hypotonic solution to the hypertonic solution

Diffusion always spontaneously occurs in the direction from an area of high concentration to an area of low concentration

Entropy demands that osmosis occur between two solutions of unequal tonicity until the concentrations of the two solutions are equal

Osmotic pressure (symbolized as capital pi, Π) results from the potential drive for the concentration of water to equalize

Osmotic pressure is a colligative property, and the osmotic pressure of a solution increases with increasing solute concentration

The relationship between osmotic pressure and concentration is given by:

ΠV = nRT

If the volume is in liters and we divide both sides of the relationship by volume, we get:

Π = MRT

where Π is the osmotic pressure, M is the molarity of the solute particles, R is the ideal gas constant, and T is the absolute temperature

Question 26

Colloids

Answer 26

Similar to solutions in that they consist of one phase uniformly dispersed in a second phase

Examples: milk, blood, paint, and jelly

Not true solutions because the particles in the dispersed phase are not the size of molecules or ions

Particles in a colloid range in size from 10 nm to 200 nm

Colloidal particles cannot be filtered and do not settle out of solution

Colloids can be stable for years if they are stored under controlled conditions

Colloids exhibit the Tyndall effect, whereas solutions do not

Particles of a colloid are large enough to scatter light passing through

Particles in a true solution are too small to scatter visible light, so solutions do not exhibit the Tyndall effect

Question 27

Chemical Equilibria

Le Châtelier’s Principle

Answer 27

States that equilibrium is a good thing, and nature strives to attain and/or maintain a state of equilibrium or homeostasis

Question 28

Chemical Equilibria

Changing Concentration

Answer 28

If you add products, the equilibrium will shift toward reactants

If you remove products, the equilibrium will shift toward products

The system readjusts to counteract whatever change made

Question 29

Chemical Equilibria

Changing Temperature

Answer 29

Increasing temperature favors endothermic processes

Question 30

Chemical Equilibria

Changing Volume and Pressure

Answer 30

Significantly impacts equilibrium reactions only when at least one of the reactants or products is a gas bc liquids and solids are not compressible

Decreasing volume increases pressure -> smaller number of gas particles

Question 31

The Equilibrium Constant

Answer 31

A system is in a state of equilibrium when there is a balance between reactants and products

This balance is defined by thermodynamic parameters, namely bond strengths and the intermolecular forces between all the molecules in the system

The equilibrium constant (K) is the numerical description of that balance

K is equal to the product of all of the molar concentrations of the products, each raised to the power of their stoichiometric coefficients, divided by the product of the molar concentrations of the reactants, each raised to the power of their stoichiometric coefficients

Question 32

Subscripts

Answer 32

The equilibrium constant (K) is often appended with a subscript that denotes the type of equilibrium reaction

Keq is a generic equilibrium constant

Ka is an equilibrium constant governing the ionization of weak acids

Kb is an equilibrium constant governing the ionization of weak bases

Ksp is an equilibrium constant governing the solubility of sparingly soluble compounds

Question 33

Meaning of K

Answer 33

As K increases, the reaction tends to increasingly favor products and the forward reaction becomes more favorable

As K decreases, the reaction tends to increasingly favor starting materials, and the reverse reaction becomes more favorable

Question 34

Solids and Liquids

Answer 34

Pure solids or liquids comprise a different phase from where reactions in aqueous media occur

The concentration of pure solids and liquids is a constant value (or very nearly so), and these constant values for concentration are included with the equilibrium constant value

The concentration of solids, liquids, and water (as a solvent) do not appear explicitly in the equilibrium constant expression

Question 35

Reversing a Reaction

Answer 35

When you reverse the equation for a chemical reaction, Kforward is the reciprocal of Kreverse

Kforward = 1/Kreverse

Question 36

Definition of Acids and Bases

Answer 36

Arrhenius definition (most operational definition)

Acid–species that increases the hydronium ion (H3O+) concentration in an aqueous solution

Base–species that increases the hydroxide ion (OH–) concentration in an aqueous solution

Brønsted2 definition (most generally useful definition)

Acid–species that donates a hydrogen ion (H+) to a base

Base–species that accepts a hydrogen ion (H+) from an acid

Question 37

Conjugate Acid-Base Pairs

Answer 37

The charge on the conjugate acid is always one greater than the charge on its conjugate base

When an acid gives away its hydrogen ion to a base, the acid is converted into its conjugate base

When a base accepts a proton from an acid, the base is converted into its conjugate acid

In generic form, we can express this process as:

HA + B → A− + BH+

Conjugate Base Ex: HNO3 -> NO3- (conjugate base)
Conjugate Acid Ex: H2O -> H3O+ (conjugate acid)

Question 38

Amphiprotic Species

Answer 38

Can behave as either an acid or a base

Ex: H2O
Base w/ HCl -> H3O+ (becomes conjugate acid)
Acid w/ HCO3- -> OH- (becomes conjugate base)

Question 39

Strong Acids

Answer 39

Acids donate protons

Very determined to foist their proton off onto a base

Essentially 100% ionized when dissolved in water, but this is not an equilibrating process, so all of the starting materials are converted into products

Strong acids are relatively rare, most acids are weak and only partially ionize in water

Ex: HCl, H2SO4, HI, HBr, HNO3

Question 40

Strong Bases

Answer 40

Bases accept hydrogen ions

In water, the strongest possible base is the hydroxide ion, OH−

A strong base ionizes essentially 100% to produce the OH − ion, so a strong base is a soluble ionic hydroxide

Ex: LIOH, NAOH, KOH, Ba(OH)2

Question 41

Weak Acids

Answer 41

Are able to donate hydrogen ions to bases, but are less determined to do so than strong acids

When a weak acid dissolves in water, it establishes a dynamic equilibrium between the molecular form of the acid and the ionized form

Ex: HC2H3O2, H2CO3, H3PO4, NH4+

Question 42

Weak Bases

Answer 42

Are able to accept hydrogen ions from acids, but are less determined to do so than strong bases

Do not completely ionize in water to produce an equivalent concentration of the hydroxide ion, because when a weak base dissolves in water, it establishes a dynamic equilibrium between the molecular form and the ionized form

Ex: NH3, HCO3-, CO3^2-, HPO4^2

Question 43

Polyprotic Acids

Answer 43

A diprotic acid has two hydrogen ions to donate, so a diprotic acid can behave as an acid twice

A triprotic acid has three hydrogen ions to donate

The number of acidic protons is not necessarily the number of hydrogens in the molecular formula

The reason for the dichotomy of hydrogen lies in the molecular structure of acetic acid

The acidic hydrogen is bonded to a highly electronegative oxygen atom

The O—H bond is polarized toward the oxygen to a point that a base can snatch away the hydrogen as an H+ ion from the acetic acid molecule

The other three hydrogens are bonded to a carbon atom, and carbon and hydrogen have almost identical electronegativities, so those bonds are nearly nonpolar and the hydrogens have no tendencies to be removed as H+ ions

Question 44

Acid and Base Strength: Ka and Kb

Answer 44

Some acids are stronger than others

A stronger acid is more determined to give its proton to some base

A stronger base is more determined to take a proton from some acid

When a strong acid dissolves in water, it dissociates completely

All other acids are weak acids

The relative strength of a weak acid is quantified by the equilibrium constant Ka governing the ionization of the weak acid

A larger value of Ka means a stronger acid

Question 45

Acid/Base Strength of Conjugate Acid–Base Pairs

Answer 45

The stronger the acid, the weaker its conjugate base

The stronger the base, the weaker its conjugate acid

General guidelines
The conjugate base of a really strong acid has no base strength
Ex: HCl is a strong acid; Cl- phase no base strength

The conjugate base of a weak acid has base strength
Ex: Acetic acid is a weak acid; acetate acid has base strength

The conjugate acid of a weak base has acid strength
Ex: Ammonia is a weak base; ammonium ion behaves like an acid in water

Question 46

Acid-base reactions

Answer 46

Involve a transfer of a hydrogen ion from the acid to the base

In order to predict the products of an acid–base reaction:

Identify which is the acid and which is the base

Move an H+ ion from the acid to the base, converting the acid into its conjugate base and the base into its conjugate acid

Any acid–base reaction has two acids and two bases:
One acid and one base on the reactant side

Conjugate acid and conjugate base on the product side

The base almost always has a lower (more negative) charge than the acid

Also, hydrogen is almost always the first atom listed in the formula of an acid

The reaction equilibrium always favors the formation of the weaker acid

Look up the Ka’s for the reacting acid and the conjugate acid of the reacting base

Question 47

Measuring acidity

The p-Function

Answer 47

The p in pH is a mathematical operator that means the negative logarithm of, and the H in pH means hydrogen ion concentration, so the definition of pH is:

pH = −log[H+]

p-function operator used to express the concentrations of many ions, but the meaning of the p is the same in every case—take the logarithm of the concentration and then change the algebraic sign

A logarithm function is a way to map a vast range of values onto a much smaller set of values

To apply the p-function, take the logarithm of the [H+] concentration and then change the sign

The value of the pH will be the same as the absolute value of the exponent when the first part of the scientific notation is exactly 1

pH values have no intrinsic units—logarithms represent “pure numbers”

Each change of 1 pH unit means the hydrogen ion concentration is changing by a factor of 10, so small changes in pH correspond to much larger changes in acidity level

Removing the p-function is accomplished by changing the sign of pH and then taking the antilog

Question 48

Self-Ionization of Water

Answer 48

Water has some very weak acid–base properties, and therefore sets some limits on the parameters of the pH scale

A tiny fraction of water molecules dissociates or ionizes into a hydrogen ion and a hydroxide ion

H2O ⇄ H+ + OH−

The equilibrium constant that governs this equilibrium is called Kw

At 25°C, Kw = 1.0 × 10−14 so pKw is 14.00

Since water is a pure liquid, the concentration of water does not appear in the equilibrium constant

Kw = [H+] [OH−] = 1.0 × 10 −14 at 25°C

In pure water, the concentrations of the H+ and OH− ions are equal

[H+] = [OH−] in pure water

The pH of pure water is 7.00 because that is the negative logarithm of the hydrogen ion concentration that is generated by the self-ionization of water

Question 49

Relationship Between pH and pOH

Answer 49

Because pH and pOH are derived from the ionization of water, there is a fixed relationship between them

The pH plus the pOH of any aqueous solution (at 25°C) always adds up to 14.00:
14.00 = pH + pOH

Question 50

pKa and pKb

Answer 50

The equilibriums constants for acids and bases are commonly presented as p-functions

The pKa and pKb of a conjugate acid–base pair sum to give 14.00:

pKa + pKb = 14.00

Question 51

The Key Relationships

Answer 51

To solve pH calculation problems, you need to be conversant with six key relationships:

pH = −log [H+]

pOH = −log [OH−]

[H+][OH−] = Kw = 1.00 × 10−14

pH + pOH = pKw = 14.00

pKa + pKb = 14.00

KaKb = Kw

Question 52

Calculating the pH of a Strong Acid Solution

Answer 52

Strong acids completely ionize in water, which means every mole of strong acid falls apart into an equal number of moles of hydrogen atoms

[H+] is equal to the formal concentration of the acid

Question 53

Calculating the pH of a Strong Base Solution

Answer 53

Strong bases completely ionize in water, which means every mole of strong base falls apart into an equal number of moles of hydroxide ions, except for Ba(OH)2, which gives 2 moles of hydroxide ions per mole

[OH−] is equal to the formal concentration of the base

Be careful when calculating the pH of a basic solution because the first number that comes out of your calculator is going to be pOH, not pH

pOH= -logOH
pH = 14 - 0.82 = pOH

Question 54

Calculating the pH of a Weak Acid Solution

Answer 54

Weak acids and bases do not ionize completely, so we must use the equilibrium constant expression to find the pH of weak acid solutions

Question 55

Calculating the pH of a Weak Base Solution

Answer 55

Involves exactly the same process as calculating the pH of a weak acid

Question 56

pH of Salt Solutions

Answer 56

Acids and bases react to give salts and (usually) water

The pH of a salt solution depends on the acid/base strength of the acid or base from which it was derived

Question 57

Salts of Strong Acids/Bases

Answer 57

Very strong acids have conjugate bases with no base strength, so these ions do not change the pH of a solution

Question 58

Salts of Weak Acids

Answer 58

Salts of weak acids are bases, and most acids are weak acids, so the conjugate bases of these acids have some appreciable base strength

The vast majority of anions increase the pH of a solution

Question 59

Salts of Weak Bases

Answer 59

Salts of weak bases are acids

Many medications are organic amines, or alkaloids, which are weakly basic organic compounds that are generally not very soluble in water

They are converted to their conjugate acid form by reacting with a strong acid (such as HCl)

Question 60

Extreme Concentrations

Answer 60

Be wary when concentrations get below 10^−3 molar, or when the concentrations aren’t that different from the Ka values

Example: What is the pH of 1.0 × 10^−8 M HCL

If you use your calculator to determine the negative log of 1.0 × 10−8, you get an answer pH = 8.0, which is incorrect

You cannot be totally complacent about these kinds of calculations, especially when the concentrations become very dilute

Question 61

Other acidic species

Answer 61

Nonmetal oxides dissolve in water to give acid solutions

The most physiologically important example is carbon dioxide

Buildup of carbon dioxide in the blood results in acidosis

In cellular tissue, where the carbon dioxide concentration is relatively high, the increased acidity slightly alters the structure of hemoglobin and facilitates the release of oxygen

Carbon dioxide is a nonmetal oxide because it is a compound composed of a nonmetal and oxygen

Nonmetal oxides are sometimes called acid anhydrides because they are produced by stripping water from an acid

When carbon dioxide dissolves in water, it combines with a water molecule to give carbonic acid
CO2 + H2O ⇄ H2CO3

When the carbonic acid forms, it dissociates according to its acid strength
H2CO3 ⇄ H+ HCO−3

So, when CO2 dissolves in water, the pH drops

Question 62

Buffers

Answer 62

A pH buffer is a solution that resists changes in pH

It contains a weak acid (HA) and its conjugate base (A−) or a weak base and its conjugate acid

Buffer solutions resist change in pH

If a strong base is added to a buffered solution, the weak acid in the buffer HA reacts with the hydroxide ion to give water and the weak base A−
HA + OH− ⇄ H2O + A−

This results in converting a strong base OH− into a weak base A−

The pH increases, but not by much

If a strong acid is added to a buffered solution, the weak base in the buffer (A− ) reacts with the H+ ion to give HA
A− + H+ ⇄ HA

This results in converting a strong acid H+ into a weak acid HA

The pH decreases, but not by much

Question 63

Calculating the pH of a Buffer

Answer 63

The pH of a buffer is determined by the acid strength of HA

As the acid strength of HA increases, the pH range maintained by a buffer system based on HA decreases

Equation for the acid ionization of HA:
HA ⇄ H+ + A−

The equilibrium constant expression for this equilibrium is:
Ka = [H+] [A-] / [HA]

The equilibrium state can be achieved from an infinite number of starting points

The Henderson–Hasselbach equation, or buffer equation is:
pH = pKa + log [A-] / [HA]

This equation can be used to calculate the pH of a buffer or to determine the ratio of weak acid to conjugate base at a given pH

Question 64

Dilution of Buffer Solutions

Answer 64

The pH depends on the ratio of weak base to its conjugate acid, not the numerical value of each, so a pH buffer can be diluted with water without changing the pH of the solution

Question 65

Buffer Capacity

Answer 65

To be an effective buffer, the pH must be within one pH unit of the pKa of the weak acid

pHeffective = pKa ± 1

To prepare an effective buffer, we need to identify an acid with a pKa as close as possible to the desired pH

Question 66

Alpha Plots

Answer 66

An alpha plot for a buffer (or an amino acid) shows the percentage of each component in a buffer system as a function of pH

Alpha for a given species is the percent of all the material that is present in that form

When alpha for the acid form is 75%, the ratio of acid to conjugate base is 75:25

The shape of the curves in an alpha plot is determined by the buffer equation

At low pH, most of the material is present as its acid

As the pH increases, the acid form converts to the conjugate base form

At high pH, most of the material is present in the conjugate base form

Question 67

Partial Pressure

Answer 67

Total Pressure = 1 atm = 760mmHg
50% of gas present -> 1/2 760mmHg

If proportion of molecules goes up, partial pressure goes up
As partial pressure goes up, more gas molecules enter liquid phase
Partial pressure determines likelihood of going into liquid

Factors that affect movement of gas into or out of surface layer of liquid
-solute
-solvent
-temperature (more likely to leave liquid phase if temp is high)
KH- tells likelihood of going into liquid

Concentration = Partial pressure/KH
Concentration = P/KH -> Henry's law

Question 68

Colligative Properties

Answer 68

Vapor pressure lowers
Boiling point elevation
Freezing point depression

Presence of solute interferes w/ solvent at interface btw 2 phases

Liquid has particular vapor pressure bc particles at surface of liquid can spontaneously enter gas phase

Number of gaseous particles present determines vapor pressure

Solute particles at interface occupy some of surface area, inhibiting some solvent from evaporating

Presence of solvent causes vapor pressure to decrease

When solution is raised to temp of solvent’s boiling point, solute particles block solvent molecules from going into gas phase -> increased temp

Presence of solute interferes with lattice formation -> decrease in temp

Salt added to snow, prevents ice formation because it interferes w/ lattice formation -> lower temp

Question 69

Concentration

Answer 69

measure of how much solute present per volume of solvent

Question 70

Diffusion

Answer 70

Movement of fluid from area of higher concentration to a lower concentration

Question 71

Hypertonic

More concentrated

Answer 71

Water molecules move out of cell and cause cell contraction or plasmolysis

Question 72

Hypotonic

Less concentrated

Answer 72

Water molecules move into cell and cause cell expansion or cytolysis (cell bursting)

Question 73

Isotonic

Answer 73

Equal amounts of water molecules in and out of cell. Cell neither expands nor contracts..

Equilibrium

Question 74

Bronsted-Lowry Acid

HCl

Answer 74

Proton donor

Conjugate base -> Cl-

Question 75

Bronsted-Lowry Base

H2O

Answer 75

Proton acceptor

Conjugate acid -> H3O+

Question 76

Lewis acid

HCl

Answer 76

Electron pair acceptor

Electrophile

Question 77

Lewis base

H2O

Answer 77

Electron pair donor

Neutrophile

Question 78

pH meter

Answer 78

consists of pH probe (electrode) and a volt measurement device, when calibrated displays pH of given liquid

Question 79

Buffer system:

Answer 79

Ph: 7.35-7.45
Ph < 7.35=acidosis (high H ion concentration)
Ph<7.45 = alkalosis (low H ion concentrate(ion)
CO2 in blood reacts to form carbonic acid (weak acid) -> dissociates to form bicarbonate + H ion

Most CO2 must be transformed to be transported out of the body -> form of equilibrium buffer reaction system

Too many H ions -> equilibrium reaction moves to left to form carbonic acid to prevent continued formation of H ion and prevent large change in ph
Too few H ions -> equilibrium reaction moves to right to form more CO2 converted to carbonic acid and convert to H ion to prevent drastic lowering of ph

Question 80

Henderson-Hasselbalch equation:

Answer 80

Calculate ph of buffer solution.

Buffers consist of weak acid [HA) and its conjugate base [A-].

Question 81

Ph= pka + log [A-]/[HA]

Answer 81

Find pka of weak acid, add log of concentration of conjugate base/concentration of weak acid
Particulate diagram: number of particles are counted for each molecule to determine concentration of molecules. Equal concentration results in log 1 (0). Concentration with more acid -> ph < pka value. Concentration with more conjugate base -> ph > pka value

Ph= pka + log [A-]/[HA]
pH-pka = log [A-]/[HA]
10^(ph-pka) = [A-]/[HA]

Question 82

Ka value less than 1 indicates a weak acid

Answer 82

To find pka, take -log of ka value
Log 1 = 0 
Log of # < 1 = negative number
Log of # >1 = positive number
[HA] = [A-] -> ph = pka
[HA] > [A-] -> ph < pka
[HA] < [A-] -> ph > pka

Question 83

Buffer:

Answer 83

Contains aqueous solution, contains both weak acid [HA] and conjugate base [A-]
Ka is the equilibrium constant

Acid dissociation reaction of HA (reaction is in equilibrium) H20 + HA

Question 84

Fluids

Answer 84

A fluid is any material that has the ability to flow

Both liquids and gases are considered fluids

Basic forces that cause fluids to flow

• gravity difference
• pressure difference

When fluids are placed in a container, they assume the shape of the container

Question 85

Hydrostatics

Answer 85

The study of fluids that are not moving

Important properties: density and pressure

Question 86

Hydrostatic pressure

Answer 86

Ptop = Patmosphere = Ftop/A

Force at bottom = force of the top + water

Question 87

Pressure at the Same Depth

Answer 87

Assume we have a point particle suspended in a fluid with density ρ

Since it is a point particle, it occupies no space or volume

No matter where it is placed in the fluid, the fluid will act the same, exerting the same pressure in all directions

Question 88

Pressure Versus Container Shape

Answer 88

The pressure is independent of the container shape

Question 89

Pascal’s Principle

Answer 89

When an external pressure is applied to a confined liquid, it is transmitted unchanged to every point within the fluid

• Plugged syringe w/ needle -> increased pressure on syringe not needle. Pressure increases everywhere within fluid by the same amount

Question 90

Buoyancy

Answer 90

All fluids exert a buoyant force on objects immersed in them

Upward force fluid exerts on object

Archimedes principle: buoyant force = weight of displaced fluid

Question 91

Archimedes’ Principle

Answer 91

An object immersed either totally or partially in a fluid feels a buoyant force equal to the weight of the fluid displaced

If the density of an object is greater than the density of the fluid , the object will sink
P(object>P(fluid)

If the density of the object is less than the density of the fluid , the object will float
P(object)<p> P(object) = P(fluid)
</p>

Question 92

Hydrometers

Answer 92

A hydrometer is a simple device used to measure the specific gravity of liquids such as urine or milk

A typical hydrometer is calibrated and has a weighted end to keep it upright in the liquid of interest

When placed in a liquid, it will sink until it displaces an amount of fluid exactly equal to its weight

If the fluid is dense, it will displace only a small amount of fluid and not sink very deep

If the fluid is not very dense, the hydrometer will sink deeper

The user reads the specific gravity of the liquid from the calibrated scale in the neck of the hydrometer

Question 93

Hydrodynamics

Answer 93

In general, there are two types of flow

1. Laminar flow:
   - Smooth flow
   - Characterized by an unchanging flow pattern where adjacent layers of fluid smoothly slide past each other
2. Turbulent flow
   - Flow that is not smooth
   - Chaotic and abruptly changing

Probability of turbulent flow vs laminar flow determined by Reynolds number

Question 94

Flow rate

Flow rate = area * velocity

Answer 94

The volume of fluid passing a particular point per unit time

Will have units of volume divided by time, such as gallons per minute or liters per hour

The official SI units of flow rate are cubic meters per second (m3/s)

Question 95

Speed and Diameter

Answer 95

As the diameter of a tube decreases, the speed of the fluid flowing through it increases

Ex: thumb over garden hose or blood flowing from a large vessel to smaller vessel

Question 96

Equation of Continuity

Answer 96

Velocity of a fluid flowing through a pipe is inversely related to the area of the pipe

• If the flow rate is constant, fluid flows faster through a thinner pipe

Question 97

The Bernoulli Equation

Answer 97

As the speed of a fluid increases, the pressure exerted by the fluid decreases
Must apply the Work-Energy Theorem

Wtotal = ΔKE = KEfinal − Keintial

Question 98

Venturi Tube Flowmeter

Answer 98

Device used to measure fluid speed in a pipe

Consists of a middle section with a small diameter connected on both ends to larger diameter sections via smooth transitions in order to prevent turbulence

A U-tube containing a fluid of known density connects the large and small diameter tubes

The U-tube is a manometer, which can be used to measure differences in pressure

The Venturi tube flowmeter equation can be used to determine the speed of fluid in a pipe

Question 99

Viscosity

Answer 99

Viscosity is a measure of a fluid’s resistance to flow

Fluids with high viscosity, such as honey, do not flow very readily

Fluids with low viscosity, such as water, flow more easily

The closer a fluid molecule is to a wall, the slower it moves

Adjacent regions of the fluid will have different speeds
*Required difference in flow to maintain flow is proportional to then length and average speed, and inversely proportional to the cross-sectional area

The faster regions will flow past the slower ones

Question 100

Ways to increase flow rate

Answer 100

1. increase pressure differential across the catheter or needle
2. Using a larger diameter catheter or needle
3. Using a shorter catheter or needle

Question 101

Solid

Answer 101

intermolecular forces, Van Der Waals, keep molecules in a fixed position -> lattice formation.

Heating solid -> kinetic energy of molecules increases and range of movement increases -> volume increase and expansion

Matter is not easily compressible (density not likely to change)

Question 102

Liquid

Answer 102

Heat added to solid -> range of movement of molecules is disrupted -> liquid formation

Matter is not easily compressible in this state (density not likely to change)

Question 103

Gas

Answer 103

Heat added to liquid -> kinetic energy of molecules increases until intermolecular forces can’t keep molecules close to each other -> gas formation -> free movement of molecules

Matter is easily compressed

Question 104

Reynolds number

Answer 104

R = vpdn

v= velocity
p= density
d= diameter
n= viscosity

Transition btw laminar and turbulent flow occurs when Reynolds number is about 2000

R > 2000 = turbulent flow likely
R < 2000 = laminar flow likely

Question 105

Viscosity
Units: Pa s
Pascal seconds

Answer 105

Friction btw fluid layers

Ability of fluid to resist flow

Factors affecting viscosity:

1. strength of intermolecular forces
   - greater attraction -> more viscous
2. size/shape of molecule
   - larger molecule -> more viscous
3. temperature
   - lower temperature -> more viscous

*Molecules moving from faster layer to slower layer increase speed of slower layer and vice versa.

Question 106

Units of resistance

Answer 106

Pa s m^-3

Question 107

Laminar flow

Answer 107

steady flow in one direction

occurs at lower fluid velocities

• more easily calculated

Question 108

Turbulent flow

Answer 108

swirls in eddies

occurs at higher fluid velocities

turbulent flow decreases and laminar flow more likely w/ change from larger diameter to smaller diameter of tube

• not easily calculated

Question 109

Volume flow formula

Answer 109

F = v(pi)d24

Question 110

Volume density formula

Answer 110

vd = 4F(pi)d

Question 111

Poiseuille equation

Answer 111

Describes laminar flow
If fluid has no viscosity there is no internal friction -> net force of 0
If net force is 0 -> pressure difference is 0

flow = pressure drop * (pi)r48nl

n = viscosity
l= length
r= radius

Small changes in diameter of a tube will affect the pressure drop noticeably

Question 112

Flow through tube

Answer 112

Length is greater than diameter

Question 113

Flow through orifice

Answer 113

Length is less than diameter
Equation: αd2√ ΔPρ

d= diameter
ΔP= pressure difference across it
p = density of fluid

• if flow reaches the speed of sound in fluid, rate of mass flow no longer depends on downstream pressure (it depends on upstream pressure only)

Question 114

Bernoulli’s law

Answer 114

The higher a fluid’s velocity is through a pipe, the lower the pressure on the pipe’s walls

The lower a fluid’s velocity is through a pipe, the higher the pressure on the pipe’s walls

As a fluid flows through a pipe it will not gain or lose energy -> no matter where fluid is in pipe, the energy is the same at all points

Factors of energy moving fluid

1. potential energy due to its pressure
2. kinetic energy due to its movement
3. potential energy due to force of gravity on it

If the fluid is not moving, v = 0, so the equation becomes:
P+ρgh=constant

• Equation indicates that pressure at base of column of fluid is proportional to its height and its density.
  Basis for manometers

If fluid flows through tube w/ constriction in it, velocity increases as fluid passes constriction

Pressure falls as velocity increases

Question 115

Venturi

Answer 115

A constriction w/ an entry and exit in which diameter changes gradually and maintains laminar flow

• fluid flows faster through constriction to make up for large volume flowing through the smaller area to maintain equal flow rate through pipe
• faster moving fluid = lower pressure

Question 116

Bernoulli effect

Answer 116

Reduction in pressure as fluid passes through Venturi

When gas exits constriction into wider portion of tube, linear velocity of flow decreases and pressure increases

• The slower the fluid flows, the more pressure it puts on the pipe itself

Question 117

Cohesive forces

Answer 117

Intermolecular forces btw molecules of a liquid

Molecules within liquid have equal amount of cohesive forces exhibited on them

Molecules on out portion of liquid have 1/2 as many cohesive forces exhibited on them bc they are on outer are of substance

Cause shapes to minimize and contract to strengthen intermolecular bonds of substance
Ex: water droplet

Question 118

Adhesive forces

Answer 118

Interaction of liquid and solid surface. Describe ability of a liquid to adhere to surface
Ex: water droplet on plastic stays droplet bc non polar surface of plastic does not interact with polar water molecules
But spreads on glass bc polar surface of glass spreads out and polar molecules interact w/ each to maximize interactions
Ex: meniscus concave curve in glass beaker w/ water

Surface tension: energy required to increase surface area of liquid
Ex: paperclip floating on water

Capillary action: liquid flows through material bc of attractions btw liquid molecules and surface of material
Ex: dip paper in water and fluid move upward into material to maximize hydrogen binding

Question 119

Mass flow rate

Answer 119

As water flows through pipe, it pushes along water in pipe. So mass flow rate at one part is equal to the mass flow rate at any other point in pipe

• Where the pipe is narrower, fluid will flow faster to compensate
• Fluid moving faster has less pressure than fluid moving more slowly

Ex: if one part of pipe has 1kg of fluid running through it, the narrow part of pipe also has 1kg of water running through it

Question 120

Venturi mask

Answer 120

100% O2 from wall O2 passes through green portion from tubing quickly

High velocity O2 flow -> lower than atmospheric pressure -> air from atmosphere to flow into O2 % compartment

As air flows into compartment, it mixes w/ 100% O2 and pt receives % of O2 on setting

Size of trapezoid hole determine how much air from atmosphere dilutes 100% O2 from wall.

Larger trapezoid = less wall O2 -> less concentrated O2

Ex of Venturi effect
* not precise

Question 121

Reynolds law

Predict if flow will be laminar or turbulent

Answer 121

Inertial forces/Viscous forces

Inertial forces: related to momentum of fluid; forces that cause fluid to move

Viscous forces: frictional shear forces that develop btw layers of fluid due to viscosity.

If viscous forces dominate flow -> laminar flow
Smaller number = laminar
Ex: flow of blood through vessels
Flow velocity at pipe wall - 0 (no slip condition). May velocity at center of tub -> parabolic profile is parabolic (center jets out from sides -> faster motion)
Lower pressure

If inertial forces dominate -> turbulent flow
Ex: flow of smoke from chimney
flow of air behind car traveling at high speed
Flatter velocity profile due to flow mixing
Higher pressure

Question 122

Law of Laplace

Answer 122

Pressure inside spherical bubble is equal to 2x tension divided by radius -> increased pressure tension to pull water inward while pressure pushes outward

Larger radius = larger force requirement, larger wall stress, larger metabolic demand

Aneurysm -> increased radius -> more stress on tissue + more force required to keep blood flowing

Small radius of alveoli = large pressure -> collapse without surfactant

Large radius of alveoli = small pressure -> overinflation without surfactant

Surfactant reduces surface tension (which would cause lung to close in on itself without surfactant) -> prevents alveoli collapse, evenly distributes ventilation of alveoli, improvement of lung compliance

Question 123

Wave motion

Answer 123

transfer energy through solids, liquids gases, or empty spaces (vacuums)

Frequency: # of complete waves passing a fixed point, in a given amount of time
Usually 1 second per complete wave
Measured in hertz: how many complete cycles per second
How often a wave happens

Period: time for 1 complete cycle
Measured in seconds
Time it takes for wave to occur
If it occurs repeatedly, event is periodic
Period of a day is 24hrs

Wavelength: distance btw point on one wave and same point on next wave 
symbol: lambda
measured in meters
x-rays are short
radio waves are long

Amplitude: as waves travel they create disturbance. Distance btw maximum disturbance to undisturbed position
Flat sea and incoming sea -> amplitude is height of highest point on wave to flat sea

Question 124

Transverse waves

Answer 124

Particles vibrate at 90 degrees to the direction that the energy is moving
Used to show amplitude and wavelength

Ex: waves of water (make water surface go up and down
Lightwaves

Question 125

Longitudinal waves

Answer 125

Particles of energy vibrate parallel to the direction in which wave of energy is traveling
Waves moves horizontally, back and forward
Waves close together = compressions

Waves farther apart = rarefactions

Ex: sound waves

Question 126

Doppler effect

Answer 126

Source emits sounds waves:
If source moves toward observer or observer moves toward source, frequency will increase
Frequency detected by observer is greater than the frequency of the source
Wavelengths decrease and frequency increases

If source is moving away from observer or the observer moves away from source, frequency will decrease
Wavelength increases and frequency decreases

Question 127

Inverse Square law

Answer 127

Change in intensity due to change in distance

When X-ray beam is created at anode target, its created in isotropic way meaning is its creating equally in all directions

Xray beam is also divergent -> spreads apart and is less intense as it travels through space

When tube position changes:

1. beam intensity changes
2. patient dose changes
3. receptor exposure changes (number of photons striking image receptor)

Ex: when distance from flashlight increases, light is less bright -> decrease in intensity
When distance from light decreases, light becomes more bright -> increase in intensity