NS3: CPF

Question 1

enthalpy

Answer 1

Enthalpy: heat energy in a system
Hess’s law: ΔHrxn = Σ∆Hproducts - ΣΔHreactants

Entropy, like enthalpy, increases with temperature and as a material changes phase from solid to liquid to gas.

Question 2

entropy

Answer 2

energy in a closed system that is unavailable to do work

Reactions that increase the number of moles of substances in the system (or produce more gas particles) typically increase the entropy of the system.

Entropy generally increases when a solid or liquid is dissolved in a solvent.

Entropy increases when the solubility of a gas decreases and it escapes from a solvent.

Entropy generally increases as molecular complexity increases (KOH vs. Ca(OH)2) due to the increased movement of electrons.

Question 3

how does alveoli react to inspiration?

Answer 3

The elastic recoil force of the airway and the surface tension of the water lining the airway oppose expansion of the alveoli due to the influx of atmospheric pressure. Pulmonary surfactant adsorbs to the air-water-alveoli interface, reducing surface tension and the total force resisting expansion. This increases pulmonary compliance—a measure of lung volume change at a given pressure of inspired air—and decreases the work required to expand the lungs at a given atmospheric pressure.

Question 4

importance of surfactants

Answer 4

Found on the alveoli as pulmonary surfactant
amphipathic, meaning that they contain both hydrophobic and hydrophilic regions

Work to reduce the surface tension of a liquid, thus allowing alveoli to remain inflated when the lung is compressed during respiration

Question 5

quantum numbers defined + pauli

Answer 5

Each electron in an atom is associated with four quantum numbers of n, l, ml, and ms respectively

• its position
• the subshell it is located in
• the orbital within that subshell
• the spin within that orbital

Quantum numbers narrow down exactly which electron within an atom is being described.
– the Pauli exclusion principle states that no two electrons in a given atom can have the exact same values for all four quantum numbers

Question 6

n and l q#

Answer 6

principal quantum number (n) = energy level of the electron, where higher value indicates greater energy and are farther from the nucleus

azimuthal / angular quantum number (l) = subshell of the principal quantum number in which the electron is found, with values ranging from 0 to n− 1, where l = 0 is the s subshell, l = 1 is the p subshell, l = 2 is the d subshell, and l = 3 is the f subshell

Question 7

ml and ms q#

Answer 7

Magnetic quantum number (ml) = spatial orientation of the orbital in question within its subshell, with values from -I to + I → each orbital can hold a maximum of two electrons, this means that an s subshell can contain up to two electrons, a p subshell can hold up to six electrons, a d subshell can contain up to 10, and an f subshell can hold up to 14

Spin quantum number (ms) = spin orientation of the electron, which relates to its angular momentum, with the two possible spin orientations are ms = −1⁄2 and ms = +1⁄2 ;; two electrons in the same orbital (and thus with the same ml value) are said to be paired and must have opposite spin

Question 8

electronic transitions

Answer 8

Ground state: Electrons within an atom are usually understood as occupying the lowest-energy possible orbitals

Excited state: when an atom absorbs energy, an electron can be promoted to a higher-energy orbital

• • When an electron drops from a higher-energy orbital back to its ground state, it releases energy as a photon
• • BUT – If enough energy is absorbed by an atom, an electron can be expelled from the atom entirely → the minimum amount of energy necessary to do so is known as the work function of a substance

Question 9

rutherford experiment

Answer 9

shot α-particles towards gold film in order to determine mass distribution of the atoms but found that little to no deflection occurred

concluded that the atom was mostly empty space with the positive charge located in a tiny, dense nucleus in the center of the atom

Question 10

bohr model

Answer 10

The electrons closer to the nucleus experience the greatest attractive force, so the closer an electron is to the nucleus, the greater its stability and the lower its energy level. In contrast, electrons located farther from the nucleus will have a higher energy and be less stable.

Question 11

wavelength and electron ejection relationship

Answer 11

Shorter-wavelength EMR (such as γ rays) carries much more energy than longer-wavelength EMR (such as radio waves). Therefore, we must look for the answer choice that involves the highest-energy EMR. The closer an electron is to the nucleus, the harder it is to eject. Because sp-hybridized orbitals have the most s character of almost all the hybridizations, they contain the electrons that are hardest to eject.

Question 12

what are the following particles composed of:

• gamma
• alpha
• beta
• positron

Answer 12

A gamma particle is a photon of electromagnetic energy, which does not have mass.

An alpha particle consists of two protons and two neutrons, having a mass of 4 amu.

A beta particle is the nuclear equivalent of an electron, which has a mass of approximately 1/1800 of a proton.

A positron is the antiparticle of an electron and has its same mass.

Question 13

ion and radius relationship

Answer 13

cations (positive ions) tend to have smaller ionic radii than the atomic radii of their corresponding uncharged elements. This is because an uncharged atom must lose one or more electrons to become positively charged.

On the other hand, for anions (negative ions), the ionic radius is typically larger than the corresponding atomic radius, since these species must gain electrons, and thus become slightly larger, to take on their negative forms.

The most common ionic configuration of an atom often relates to the number of electrons it must gain or lose to obtain the same electron configuration as its nearest noble gas.

Question 14

logarithms

Log values to know
log(0.01)
log(0.1)
log(1)
log(3)
log(10)
log(100)

Answer 14

A logarithm is simply the inverse of an exponent. That is, if 10A = B, then log10B = A.
pH = −log[H+] = −log[A × 10−B] = B – log A when solving for pH

Log values to know
log(0.01) = -2
log(0.1) = -1
log(1) = 0
log(3) ≈ 0.5
log(10) = 1
log(100) = 2

Question 15

SDS-page purpose

- what is this similar to

Answer 15

sodium dodecyl sulfate-polyacrylamide gel electrophoresis

Purpose: allows proteins to be separated by their mass alone by eliminating effects arising from differences in shape and charge by using a strong anionic detergent: sodium dodecyl sulfate

Question 16

sds-page steps

Answer 16

The SDS molecule denatures native proteins into their unfolded polypeptide states, which prevents protein shape from impacting the separation

Also, SDS coats the proteins with an even distribution of charge per unit mass such that the intrinsic charge of the polypeptide becomes negligible in comparison to the negative charges due to SDS → Since the protein is now highly negative, it will travel toward the positive end of the gel apparatus.

Question 17

solvents for Sn2/1 vs E2/1

Answer 17

polar protic solvents favor unimolecular Sn1 and E1 mechs bc they stabilize the carbocation

polar aprotic solvents favor bimolecular Sn2 and E2 mechs bc do not stabilize the nucleophile

memorize the solvent image on ur phone; don’t proceed until u get perfect

Question 18

nucleophilic substitution

Answer 18

common organic reaction that involves a nucleophile, or electron-rich atom, displacing a leaving group on a target molecule

unimolecular nucleophilic substitution (SN1) → takes two steps
bimolecular nucleophilic substitution (SN2) → takes only one step, thus called “concerted”

Numbering dictates how many substrates are involved in the initial step.

Question 19

Sn1 Reaction

Answer 19

1. the leaving group dissociates from the target substrate molecule, leaving behind an unstable carbocation
   - - Since the product is so unstable, this step is slow and thus rate-determining
2. the nucleophile attacks the carbocation to form a more stable product molecule → carbocation intermediate is planar, or lacks stereochemistry
   - - Can be either a “backside” or “frontside attack”
3. SN1 reactions with chiral substrates produce an even mix of enantiomers termed a racemic mixture → tend to favor tertiary substrates (as tertiary is the most stable carbocation structure)

Question 20

Sn2 Reaction

Answer 20

1. the strong nucleophile displaces the leaving group by attacking from the rear, often described as a “backside attack.”
   - - This reverse attack inverts the relative stereochemistry of the molecule.
   - - Meaning that the absolute stereochemistry (namely R vs S configuration) also invert, provided that the priority of the nucleophile matches the priority of the leaving group, which is nearly always the case
2. There is a brief instant before the LG fully dissociates where the central carbon of the substrate is at least partially bound to five substituents → this high-energy state is known as a pentavalent transition state
   - - This means that steric hindrance is a major limiting factor of SN2 reactions, with primary substrates reacting the most rapidly

Question 21

which hydrohalic acid doesn’t dissociate and why

Answer 21

All but one of the hydrohalic acids completely dissociate.

The one exception is hydrofluoric acid, which is a weak acid in aqueous solution due to its unusually high degree of covalent bonding between the fluorine and the hydrogen.

Question 22

cell potential diff btwn galvanic and electrolytic cells

Answer 22

Galvanic cells always have cell potentials greater than 0

whereas electrolytic always has less than 0

Question 23

glycosidic bonds

Answer 23

key mech thru which monosaccharides combine with each other; formed when the anomeric carbon of one sugar reacts with a hydroxyl group in another sugar via a dehydration reaction

specifically, formation of a glycosidic bond transforms the hemiacetal or hemiketal found at the anomeric carbon into an acetal or a ketal, because the –OH group that is characteristic of a hemiacetal/hemiketal is transformed into a second –OR group, which defines an acetal/ketal

Question 24

capacitance

Answer 24

measured in farads = amount of charge stored per volt = q/V

Also means that
charge (q) = VC

Electrical potential energy stored in the capacitor can also be related via the equations
E = ½ QV = ½ CV2

Question 25

heart valves

Answer 25

Tricuspid: btwn atria and ventricle
Semilunar: btwn ventricle and artery

Question 26

draw phenylalanine at physiological pH

Answer 26

no passing til perfect; image on phone

Question 27

water shell of molecules

aka “hydration / solvation”

Answer 27

water molecules will not be able to hydrogen-bond effectively with nonpolar residues, and as a result will form a highly-ordered solvation shell to minimize interactions with those residues → This highly-ordered shell represents a decrease in entropy, which is energetically unfavorable

Thus, this explains why polar residues often face into the aqueous soln since water will be able to hydrogen-bond freely with those residues → it will have relatively high entropy, which is energetically favorable

Question 28

common ion effect

- 2 scenarios

Answer 28

1) Salt dissolves (dissociates) into ions and then a quantity of one of those ions is added → equal quantity of salt precipitates out
2) ions are already present in soln when salt is introduced → salt dissolves (dissociates) less

Question 29

Ksp

Answer 29

A large Ksp suggests that a substance is more soluble than a substance with a lower Ksp.

Question 30

PE of imperfect vs perfect springs

Answer 30

potential energy stored in a spring can be expressed as PEelastic = ½kx2, where k is a spring constant that is specific for each spring and can be thought of an indicator of its stiffness and x is how far the spring has been stretched or compressed. Thus, the more a spring is compressed, the more energy will be stored in it, and energy increases nonlinearly with compression or extension.

Perfect spring: all energy conserved
Imperfect spring: some loss of energy lost due to inefficiency

Question 31

hooke’s law
periodic motion of springs
one work equation

Answer 31

Hooke’s Law: F = kx, where k is the spring constant

Springs can also be used to generate periodic motion:
T that separates adjacent peaks on a graph of periodic motion is known as the period, and for a mass on a spring undergoing periodic motion, T = 2π√(m/k), where m is the mass and k is the spring constant.

W = F⋅d⋅cos(θ)

Question 32

what does “absorbing” KE mean?

Answer 32

When something “absorbs” kinetic energy, it converts it into elastic potential energy → look at question statement to determine whether heat is lost as energy or through an imperfect spring, otherwise we can assume that it is a perfectly elastic process here for the sake of simplicity.
Elastic PE (of a spring): PE = (1/2) kx2

But since PE and KE are interconverted as something “absorbs” the energy (ie an individual running changes the KE they get from running into the PE they get when they bounce off the ground), we can write this formula as KE = (1/2) kx2, which can be rearranged to yield k = 2 KE/x2.

Question 33

charle’s law

Answer 33

direct relationship between the volume of an ideal gas and its temperature, when pressure is constant

Thus, V1/T1 = V2/K2