NS5: CPF

Question 1

enthalpy: which is more thermodynamically favorable, lower or higher value?

Hess’ law

entropic penalty

Answer 1

heat energy of a system, delta H

The lower the enthalpic barrier, the more thermodynamically favorable the reaction is.
– Recall that Hess’ law states that ΔHrxn = Σ∆Hproducts - ΣΔHreactants

Entropic penalty: thermodynamically disfavored formation of polar solvent molecules around surface-exposed hydrophobic portions of a molecule.

Question 2

Entropy increases when … (4)

Answer 2

The number of moles of substances in the system increase

When a solid of liquid is dissolved in a solvent

When the solubility of a gas decreases and it escapes from a solvent

When molecular complexity increases, due to the increases movement of electrons

Question 3

Spontaneity

Answer 3

predicted by the equation ΔG = ΔH – TΔS, where ΔG is the Gibbs free energy and ΔS is change in entropy. Negative values of ΔG indicate spontaneity.

As a thermodynamic value, ∆G is also closely related to equilibrium via the equation ∆G°rxn = −RTln Keq

Specifically, an equilibrium constant (Keq) > 1 indicates that the reaction favors the production of products, which corresponds to a negative ∆G
– It then follows that when Keq < 1, ∆G > 0, and this positive ∆G indicates a nonspontaneous reaction.

Question 4

Vitamins

which are water v lipid soluble

Answer 4

non-macronutrient compounds that are vital for healthy functioning and cannot be synthesized in adequate quantities by the body, meaning that they must be obtained from external sources

Water soluble: B and C
Lipid Soluble: A, D, E, and K

Question 5

specific vitamin functions

Answer 5

Vitamin B is used to create coenzymes used by the body such as thru thiamine, riboflavin, biotin, pyridoxine, and some others that aid in enzymatic functions.

Vitamin C is useful in generating connective tissue, which is why vitamin C deficient people have connective tissue disorders like scurvy.

Vitamin A plays a key role in vision, growth and metabolism.

Vitamin D in calcium and phosphate absorption from the gastrointestinal tract

Vitamin E is an antioxidant and neutralizes reactive oxygen species

Vitamin K promotes coagulation and is important for bone health

Question 6

explain oil-water IMFs

Answer 6

The Van der Waals forces that exist between molecules of water and of oil are predominately of the induced dipole-dipole type. Here, a small, temporary dipole is induced in molecules of oil by the permanent dipole of water, resulting in a weak attraction between the molecules. This is a weaker interaction than the hydrogen bonding that predominates in the interaction between water molecules.

Question 7

amphiphiles + example

Answer 7

Amphiphiles are chemical compounds that possess both hydrophilic and hydrophobic components.

Eg. Phospholipids are triacylglyceride derivatives with two nonpolar fatty acid “tail” regions and a hydrophilic phosphate-containing “head.”

Question 8

Conditions of the Doppler effect

Answer 8

The Doppler effect is used to analyze MOVING objects or fluids. A Doppler shift will be registered only if the fluid is moving relative to the source of the sound (the device). More specifically, at least some component of the fluid’s velocity must exist in the same directional plane as the wave’s velocity (otherwise, the device will register the fluid as not moving at all), and this component must be different from the velocity of the sound source.

Eg. If observer and source of sound are moving at the same velocity, then no shift will be observed. Additionally, if neither is moving at all, then no shift will be observed.

Question 9

presbyopia vs myopia

how are they fixed

Answer 9

Presbyopia (far-sightedness) is the image is formed behind the retina rather than on the retina → fixed with a converging (convex) lens that will converge light rays before they can pass the retina and focus light closer to the retina.

Myopia (near-sightedness) is the image formed before the retina → fixed with a diverging (concave) lens that would spread out (diverge) the light before it reaches the retina, allowing it to pass through the cornea and be appropriately focused on the retina

Question 10

Mirrors + 3 types

Answer 10

substances from which light rays only reflect, without any significant absorbance or refraction

Plane / linear mirror: a ray of light that hits it perpendicularly will be bounced back in the same direction; however, angled hits will reflect in the same but opposite angle to the normal

Concave mirrors: have an inward curve, causing incident light rays to CONVERGE on each other upon reflection

Convex mirrors: have an outward curve, causing incident light rays to SCATTER outwards

Question 11

how do lenses differ from mirrors?

+ 2 types of lenses

Answer 11

Lenses differ from mirrors in that light passes thru lenses, which are typically made of glass. Thus, light is refracted both upon entering and exiting a lense.

Convex lenses cause rays to CONVERGE

Concave lenses cause them to DIVERGE

** note that it is opposite to mirrors

Question 12

Thin Lens Equation

Answer 12

1/o + 1/i = 1/f, where o is the object distance, i is the image distance, and f is the focal length

Real images: formed by real light rays → use POSITIVE signs
– Will be on same side for mirrors, opposite side for lenses

Virtual images: formed by incidence light rays → use NEGATIVE signs
– Will be on opposite side for mirrors, same side for lenses`

Question 13

Magnification

Answer 13

defined as –i/o, or the negative ratio of the size of the image to the size of the object

A negative magnification value means that the image is inverted compared to the object, which corresponds to it being real.
– recall that real images will be observed on the OPPOSITE SIDE in lenses

Question 14

when light goes from one medium to another, it ______

Answer 14

changes speed

Note: Since the speed of light in a vacuum (c) is the maximum speed at which normal matter can travel in the universe, it is convenient to define the speed at which light passes through a medium with reference to the speed of light in a vacuum.

Thus, refractive index (n) of a given material is defined as n = c/(v of material)

eg. for vacuums and air, n =1
eg. for window glass, n = 1.52

Question 15

Snell’s Law

Answer 15

n1 * sin(θ1) = n2 * sin(θ2) where θ is defined with reference to the normal, or a line that runs perpendicular to the surface on which the wave is incident

Recall that when light passes from one medium to another and changes speed, it bends; this equation lets you calculate exactly how much

Question 16

define the following:

• critical angle

- total internal reflection

Answer 16

Critical angle = As the angle of the incident ray (θ1) increases, there will come a point where the angle of the refracted ray (θ2) reaches 90°

Total internal reflection: If we increase the angle beyond the critical angle, the light can no longer refract at all. Instead, all the light rays are reflected within the original medium

Question 17

gaseous solubility ____ as temperature ____

why?

Answer 17

Gaseous solubility DECREASES as the temperature INCREASES, due to an increased desire to evaporate or escape the solute.

Question 18

binary fission + steps

Answer 18

main method through which bacteria reproduce → basically mitosis

Requires ATP, therefore aerobic bacteria divide faster than anaerobic

Three steps:

1. Replication: chromosome is duplicated while the cell grows
2. Segregation: chromosomes are pulled towards different sides of the cell and the cell envelope / cell wall begins to grow towards the middle of the cell
3. Separation of the two daughter cells

Question 19

bacterial growth timeline (4 phases)

Answer 19

Exponential growth process occurs when the bacteria are introduced to a new environment

Lag phase: process by which bacteria adapts to this new environment

Log phase: rampant growth that rapidly depletes available resources

Stationary phase: growth ceases as environment is unable to sustain exponential growth

Death phase: complete exhaustion of resources eventually leads to bacterial death

Question 20

what can change an equilibrium constant

Answer 20

temperature

Question 21

Nuclear magnetic resonance (NMR) spectroscopy

resonance frequencies

Answer 21

places sample into a magnetic field

If the sample has a nuclear spin due to an odd number of protons or neutrons, then it will be affected by the magnetic field. The atomic nuclei will align with the field (a lower-energy state) or against the field (a higher-energy state). The frequency of the transition between these states, or resonance, is measured by NMR.

RESONANCE FREQUENCIES are chemical shifts ranging from zero on the far right to positive values on the far left. — A shift of zero is arbitrarily assigned to the peak corresponding to tetramethylsilane (TMS) as a reference point

• • Peaks that are shifted to the right are said to be located upfield
• • peaks that are shifted to the left are said to be located downfield

Question 22

H NMR

• definition
• equiv H’s
• multiple equiv H’s

Answer 22

spectrum can range from 0–12 ppm; location depends on the extent of shielding or deshielding experienced by 1H nuclei, which varies by functional group

Equivalent hydrogen atoms are protons that exist in the same magnetic environment; such protons do not differ in any measurable way, so they correspond to only one peak on the spectrum

If a peak corresponds to multiple equivalent hydrogen atoms, the area under that peak will be proportionally greater than the area under a peak that corresponds to a single hydrogen atom. In other words, the peak area (or integration) directly correlates to the number of protons represented by that peak.

Question 23

H NMR

- splitting

Answer 23

each signal is affected by protons on atoms adjacent to the carbon to which the proton is attached. Splitting patterns are predicted the n + 1 rule, which states that any peak will be split into a number of smaller peaks equal to the number of adjacent hydrogen atoms plus one.

For example, if a hydrogen atom is positioned on a terminal carbon adjacent to a carbon bound to one additional hydrogen atom, the peak that represents the first hydrogen atom will be split into a doublet (1 adjacent hydrogen atom + 1 = 2).

Question 24

what halogen has H-bonding

Answer 24

HF is the only halogen to have hydrogen bonding because it has a high level of electronegativity.

Question 25

Chromatography

• definitions (2)
• interactions
• example

Answer 25

Stationary phase: solid phase that facilitates travel

Mobile phase: usually contains a common feature with target molecules such that interaction will slow down their travel

Molecules of interest in the mobile phase will interact with the stationary phase with different levels of intensity. Molecules that interact more strongly with the stationary phase will take longer to pass through it, whereas molecules that interact more weakly with the stationary phase will pass through it more quickly

Eg. If the stationary phase has a net positive charge, then oligopeptides with negative charges will be attracted to the stationary phase and will move more slowly through the column. In contrast, positively charged molecules will interact less with the stationary phase, thus moving faster.

Question 26

Ka and Pka / Kb and Pkb

• relationship
• conjugate strength
• acid strength
• dissociation strength

Answer 26

The Ka and pKa values of acids are inversely related to each other (since pKa = -log [Ka], and to corresponding Kb and pKb values of their conjugate bases.

The strongest conjugate base will be produced by deprotonating the weakest acid.

As pKa values decrease, acid strength goes up.

The more acidic a compound it, the more readily it dissociates.

Question 27

Strong BASES that end in “-ide” (4)

Answer 27

NAOH, Sodium hydroxide
LiOH, Lithium hydroxide
KOH, Potassium hydroxide
CsOH, Cesium hydroxide

Question 28

Strong ACIDS that end in “-ic acid” (6)

Answer 28

HCl, Hydrochloric acid
HBr, Hydrobromic acid
HI, Hydroiodic acid
H2SO4, Sulfuric acid
HNO3, Nitric acid
HClO4, Perchloric acid

Question 29

Ka / Kb / pH / pOH relationship

Answer 29

look at equation for stoichiometry

Ka = [H+][A−]/[HA] and [H+] = 10-pH

pOH = -log[OH-]

In water at 25°C, Ka•Kb = 10-14. Given this, Kb = 10-14/Ka
– also pH + pOH = 14

Question 30

open / closed / isolated system

Answer 30

Open system: matter and heat energy can be exchanged btwn surroundings and system

Closed: only heat energy, not matter, can be exchanged btwn surroundings and system

Isolated: neither matter nor heat energy can be exchanged btwn surroundings and system

Question 31

ozonolysis

Answer 31

cleavage of an alkene or alkyne with ozone (O3) that results in the multiple carbon–carbon bond being replaced by a double bond to oxygen (carbonyl)

Question 32

Sound

• composition
• speed
• frequency

Answer 32

made up of longitudinal, compressive waves, thus it has properties of speed, wavelength, and frequency; also produced by the displacement of air caused by the movements of and interactions between various objects in the environment.

Speed of sound is not constant → sound waves move more quickly through relatively non-compressible, or stiffer media; it also increases with temperature

Frequency is related to pitch, or how we perceive sounds as high or low, with high-frequency sounds corresponding to high pitch and low-frequency sounds corresponding to low pitch

Question 33

intensity of sound

Answer 33

measure of the power delivered by sound over a given area → units being W/m2, or a decibel (dB)

The decibel scale is a logarithmic scale expressing the intensity of a sound as its ratio to that of the smallest detectable sound intensity I0
dB = 10log(I/I0), where I0 is 1 × 10−12 W/m2

Question 34

A single sports fan is capable of yelling at an intensity level of 80 dB from a given distance. If 10,000 similar fans were all yelling from the same distance, which of the following would be closest to the observed intensity level?

Answer 34

10,000 fans would be capable of yelling at an intensity 10,000, or 104, times greater than the single fan alone.

According to the decibel scale, this would correspond to an increase of 40 dB, because 10log(10-4) = 40.

Thus, we would perceive an intensity level of 120 dB from the crowd of 10,000.

Question 35

standing waves

Answer 35

take place when waves propagate through media that are physically constrained in one way or another

sinusoidal in shape and have areas where there is no displacement (aka NODES; corresponding to what would look like y = 0 on a standard sine curve graph) and areas with maximal displacement (aka ANTI-NODES, corresponding to the amplitude of the resultant standard waves).

wavelength of a standing wave in a closed-closed or open-open space is given by the following equation: λ = 2L / n where λ = wavelength, L = length and n = harmonic

Question 36

waves

• mechanical (2)
• electromagnetic

Answer 36

formed when a pattern of periodic motion (or oscillation) propagates through space

Mechanical waves: involve the actual physical motion of particles; aka compression waves bc essentially results in a pushing-and-pulling motion → eg. sound

• • Transverse: direction of the displacement of the particles is perpendicular to axis through which the wave propagates
• • Longitudinal: … parallel …
• • The amplitude of a mechanical wave refers to how far particles are displaced from baseline.

Electromagnetic waves: can move through vacuum → eg. light

Question 37

what are the universal properties for all waves and how are they related?

Answer 37

v = λf

wavelength (λ): the spatial interval over which a waveform repeats itself

propagation speed (v): the speed with which a wave signal spreads through space

frequency (f): the number of wavelengths that go by per second → also 1/T

period (T): the time that separates adjacent peaks

Question 38

Capacitance is directly proportional to _____ and inversely proportional to _____, therefore ____.

Answer 38

Capacitance is directly proportional to area but inversely proportional to the distance between the two sides of the capacitor.

Thus, decreasing the width of the membrane would decrease the distance btwn the two sides, thus actually increasing capacitance.

Question 39

specific gravity

volume

Answer 39

Specific gravity relates the density of an object (or fluid, as is the case here) to the density of water, which is 1000 kg/m3. Note also that 1000 L = 1 m3.

Volume = mass / density