Chem/Phys Flashcards

Question

What is the difference between a pyranose and a furanose?

Answer 1

A pyranose is a five-membered ring whereas a furanose is a six-membered ring.

Answer 2

Left means Up and Right means Down when converting positiong of hydroxyl (-OH group) from Fischer to Haworth ![]()

Answer 3

Carbon 4 is the location of the hemiketal. A hemiketal is a carbon bound to two -R groups, an -OR, and an -OH. The general structure of a hemiketal is shown below. ![]()

Answer 4

The C1 carbon does represent the carbonyl carbon from the open-chain form of ribose, and the hydroxyl attached to C4 is the nucleophile from the nucleophilic addition reaction. ![]()

Answer 5

The alpha anomer on a Haworth structure features a hydroxyl group oriented down trans to the CH2OH. The anomeric carbon (the only carbon bonded to two oxygens) in this Haworth projection features a hydroxyl group oriented down opposite (trans) to the CH2OH group, making this molecule alpha. This is alpha-galactopyranose. ![]()

Answer 6

**Hemiacetal has one** R-group directly bonded to the anomeric carbon whereas the **Hemiketal has two** R-groups directly bonded to the anomeric carbon. ![]()

Answer 7

The hydroxyl group on carbon 5 attacks the carbonyl group. The oxygen from this hydroxyl group becomes a member of the ring, so it is neither above nor below the ring in the Haworth projection of the sugar. ![]()

Answer 8

Conductivity and resistivity depend on material properties of an object, while conductance and resistance also depend on the length and cross section surface area of an object (which make it easier and harder for an electron to move through an object, respectively).

Answer 9

Electric potential energy is similar to gravitational potential energy, in that both are the amount of stored energy for a total amount of mass/charge. Electric potential, on the other hand, is normalized to per unit charge and has units of joules per charge, or volts.

Answer 10

Equipotential lines indicate locations in an electric field where the electric potential is constant, but not necessarily the strength of the electric field. If the strength of the electric field is not constant, then the strength of electric force it will exert on a charge is not constant either.

Answer 11

A greater conductivity means that a material has a greater ability to allow for the flow of electrons. Conductivity is signified by the Greek letter sigma, or σ. Resistivity is the property of a material which determines how well an object resists the flow of electrons. It is signified by the Greek letter rho, or ρ. ρ = 1/σ and σ = 1/ρ Conductivity is the inverse of resistivity, and conductance is the inverse of resistance. Conductivity and resistivity depend on material properties of an object, while conductance and resistance also depend on the length and cross section surface area of an object (which make it harder and easier for an electron to move through an object, respectively).

Answer 12

The strength of an electric or gravitational field increases linearly with charge and mass, respectively. Two masses will exert a gravitational force on one another. Likewise, two charges will exert an electric force on one another.

Answer 13

J/C The units of force are newtons. Newtons times meters equals joules – therefore, joules divided by meters is an appropriate unit to describe force.

Answer 14

J Electric potential energy describes a change in energy of an object as it moves through an electric field, described by joules.

Answer 15

J/C Electric potential is the amount of energy per unit of charge needed to move a charged object through a field. This can be described by joules per coulomb.

Answer 16

N/C Electric fields extend outwards from an electric charge. The value for electric field will tell you how many newtons of force the electric field will exert on an object per unit of charge, at some point in that field.

Answer 17

Propanoic acid \> propanethiol \> propanol \> propanone (from most acidic to least acidic)

Answer 18

No, secondary alcohols can only oxidize into ketones.

Answer 19

PCC is a Weak oxidizing agent which means it can only oxidize a primary alcohol or secondary alcohol once to a ketone and not twice into a carboxylic acid.

Answer 20

Least to most acidic: ethane, ethanol, water, ethanoic acid Carboxylic acids typically have pKa values anywhere in the 2-5 range

Answer 21

Esters can be created by reacting a carboxylic acid or carboxylic acid derivateive with an alcohol.

Answer 22

london dispersion forces, hydrogen bonds, covalent bonds, ionic bonds (weakest to strongest)

Answer 23

**Diamagnetic** atoms have no magnetic spin whatsoever. **Ferromagnetic** materials contain atoms with uniform and non-random spin. **Paramagnetic** materials contain atoms with random/non-uniform magnetic spins. (The only time the magnetic spins of paramagnetic atoms are purposefully aligned with one another is when an external magnetic field is applied to them.)

Answer 24

No, they will both have the same "induced" direction so it is not possible to tell them apart.

Answer 25

Mass, charge and velocity

Answer 26

Carboxylic acid \> Alcohol \> Aldehyde \> Alkane The boiling point of a liquid increases as intermolecular forces increase and more energy is required to separate molecules. Carboxylic acids have the strongest intermolecular forces, because they form two hydrogen bonds per molecule via their CO2H; next is pentanol, which can hydrogen bond using its OH; then pentanal, an aldehyde with dipole-dipole interactions due to its polar C=O; and finally pentane, a simple alkane which has only London dispersion forces (Van der Waal's forces). Thus, the boiling points will follow the same order.

Answer 27

Carbanion and Carbonyl Oxygen

Answer 28

Benzaldehyde does not have any alpha protons on the carbon atom adjacent to the carbonyl carbon to deprotonate.

Answer 29

The alpha carbon of the enolate acts as a nucleophile while the carbonyl carbon of the neutral aldehyde would act as an electrophile when an aldehyde is in a solution with a strong base.

Answer 30

Butanal has a higher oxidation state than butanol. As a carbon gains bonds to oxygen, its level of oxidation increases. The carbonyl carbon of butanoic acid has three bonds to oxygen; the carbonyl carbon of butanal has two; the alcohol-bearing carbon of butanol has one; and butane has zero carbon-oxygen bonds.

Answer 31

Resisitivity is a property inherent to a material. It is resistance that changes with shape, not resistivity.

Answer 32

gas, liquid, amorphous solid and crystalline solid (decreasing randomness)

Answer 33

Yes. Surface tension is the tension created at the liquid’s surface by the **intermolecular** forces between molecules, not the intramolecular forces. Surface tension represents the amount of energy required to increase the surface area of a liquid. Since liquid density affects the liquid’s weight and surface area, it would also then affect surface tension.

Answer 34

Yes since T is delta T. Q = mc∆T In this equation, c is the specific heat capacity of a substance, which is the amount of heat required to raise the temperature of one unit mass of substance by one degree. The SI units for specific heat capacity are J/g·K or J/g·°C. For example, the specific heat capacity of water is 4.186 J/g°C.

Answer 35

Viscosity is the property of liquids by which they are resistant to flow, or the resistance to deformation by shear stress. On the molecular level, viscosity is caused by friction between layers of the fluid that are in motion relative to each other. Thus, fluids that have higher viscosity are more resistant to flow than those with lower viscosity. Since olive oil is more viscous than whole milk, beaker A will be emptied first. Surface tension is not a property of a liquid’s resistance to flow. Surface tension could be defined as the property of the surface of a liquid that allows it to resist an external force, due to the cohesive nature of the molecules' intermolecular forces.

Answer 36

Any conjugate base will fulfill the Lewis acid definition of a base, that of being an electron donor. This overlaps completely with the function of a nucleophile - all Lewis bases are also nucleophiles.

Answer 37

An oxygen of a carboxylate and the nitrogen of an amine The nitrogen atom in non-quaternary amines has a single lone pair. Each oxygen of a carboxylate functional group has up to three lone pairs, meaning that these atoms could serve as nucleophiles.

Answer 38

A polar aprotic solvent

Answer 39

E2 reactions require strong bases. SN2 reactions require good nucleophiles. Therefore a good nucleophile that is a weak base will favor SN2 while a weak nucleophile that is a strong base will favor E2. Bulky nucleophiles have a hard time getting to the α-carbon, and thus increase the proportion of E2 to SN2.

Answer 40

Cyclization of an aldohexose (or ketohexose, through an intermediate tautomerization step) is an example of an intramolecular **nucleophilic addition** mechanism.

Answer 41

Nucleophilic addition requires that no leaving roup be displaced in the reaction. Both **trigonal planar** and **linear** molecular geometries allow for the replacement of one bond without loss of any substituents. Carbonyl carbons are the most common case of an electrophilic site with a trigonal planar geometry, while the carbon center of a nitrile is the most common case of an electrophilic site with a linear molecular geometry. Any nucleophilic attack on a carbon with a tetrahedral molecular geometry (commonly by the SN2 mechanism) would result in nucleophilic substitution, as carbon cannot form five simultanous bonds.

Answer 42

Common types of Nucleophilic Addition reactions include: Acid-catalyzed Hemiacetal Formation, Base-catalyzed Hemiacetal Formation and Monosaccharide Cyclization.

Answer 43

Acid-catalyzed Hemiacetal Formation is done with an aldehyde and an alcohol in the presence of an acid solvent.

Answer 44

Nothing can prevent the mutarotation/interconversion of the anomeric forms of ketoses and hexoses because the nucleophilic addition towards a a trigonal planar carbonyl group may come from above or below the plane: If the attack comes from above the plane, the remaining hydroxyl must be facing the opposite way, and the alpha anomer (down-axial OH substituent) is formed. If the attack comes from below the plane, the remaining hydroxyl must again face the opposite way, and the beta anomer (up equatorial OH substituent) is formed.

Answer 45

Yes. There are different types of glycosidic bond formation mechanisms which are all types of nucleophilic substitutions. There is N-glycosidic bond formation, named after the nitrogen nucleophile. O-glycosidic bond formation involved in the formation of sugars. Finally, S-glycosidic bond formation is also biologically very relevant in attaching sugars to cysteine residues.

Answer 46

Zeroth law If two objects are in thermal equilibrium, and another object is in thermal equilibrium with one of the objects, it will also be in thermal equilibrium with the third object; if TA = TB and TA = TC, then TB = TC

Answer 47

First law Energy cannot be created or destroyed; ΔU = Q - W

Answer 48

Second law At absolute zero, entropy in a perfect crystal is 0; STemp=0 = 0

Answer 49

Third law The disorder or entropy of the universe is always increasing; ΔSuniverse = ΔSsystem + ΔSsurroundings ≥ 0

Answer 50

Work is equal to pressure times the change in volume. In this case, the change in volume is 0 and thus the amount of work performed is 0. To think about it another way, imagine a pressure volume curve depicting this process. It would be a straight vertical line, meaning it would enclose no area.

Answer 51

When work is done by the system on the environment then the work must be negative, when work is done on the system then work must be positive. Depending on the given equation of ΔU = Q - W, W must be changed to accomodate the former sign conditions.

Answer 52

Only gases are compressible

Answer 53

Boyle’s law relates the volume and pressure of a gas as follows: P1V1 = P2V2.

Answer 54

R1/R2 = sqrt(M2/M1)

Answer 55

The most ideal gases are those that experience the weakest intermolecular forces. HCl and CH4 have the least polar bonds of the gases listed and thus will exert the weakest attractive forces on other molecules.

Answer 56

Q = mc∆T In this equation, c is the specific heat capacity of a substance, which is the amount of heat required to raise the temperature of one unit mass of substance by one degree. The SI units for specific heat capacity are J/g·K or J/g·°C. For example, the specific heat capacity of water is 4.186 J/g°C.

Answer 57

Heat Capacity has nothing to do with intermolecular bonding forces. A high heat capacity means it takes more energy to change the temperature of that substance. Large bodies of water like the ocean are useful for soaking up extra heat energy without experiencing a drastic change in temperature and conversely can give off large amounts of heat for an extended period of time when the environment is colder. This creates a stabilizing effect on temperature fluctuations in coastal environments.

Answer 58

The concepts that influence enthalpy are: thermal energy, pressure and volume The formal definition of enthalpy is that it’s equal to the internal energy of a given system, plus the product of its pressure and volume. This is the same thing as saying that enthalpy is equal to the energy required to create the system, plus the work required to maintain its pressure and its volume.

Answer 59

ΔH°f rxn = ΔH° (bonds broken) - ΔH° (bonds formed)

Answer 60

A decrease in Gibbs free energy, or negative Gibbs free energy change, is associated with spontaneous reactions. These are also called EXERGONIC reactions, as the prefix “ex” tells us that Gibbs free energy is lost or decreases. On the other hand, if the products are higher in energy than the reactants, the reaction is less likely to proceed, so a positive Gibbs free energy change is associated with nonspontaneous reactions, also called ENDERGONIC reactions. For the reaction to take place, an energy barrier termed the activation energy must be overcome. This would be the endergonic, energy consuming step, of what is overall a spontaneous, exergonic reaction.

Answer 61

The reaction rate is dictated by the height of the activation barrier. The activation barrier is so high because it represents the transition state, a temporary configuration that’s very unstable and high in energy, and this is the state that the reactant molecules must transition through to become product molecules. The height of the barrier is dependent on the mechanisms and steps of the reaction, and the stability of those reaction intermediates. It will determine how quickly the reaction will proceed. For example, more stable intermediates mean a lower activation barrier and a faster reaction.

Answer 62

ΔG = -RTln(Keq)

Answer 63

While the equilibrium constant Keq is used only at equilibrium, Q (the reaction quotient) may be used for reactant and product concentrations at any point in the reaction. When Q is greater than Keq, the relative proportions of products to reactants is higher than it would like to be at equilibrium, so the reaction will want to proceed in reverse from products toward reactants to achieve equilibrium. The question stem asks us to identify a reaction that will shift towards the reactants, meaning it will run in the reverse direction. Therefore, any reaction where Q \> Keq will run in reverse to create more reactants.

Answer 64

No, the transition state is transient by definition; it will not be stable and long lasting.

Answer 65

When the concentration of a reactant doesn't change the rate but another does, the other rate will be the rate-limiting step regardless of it's order.

Answer 66

The free energy change under any set of conditions is the sum of the standard free energy change and RTlnQ, where R is the gas constant, **T is absolute temperature** and **Q represents the reaction quotient** ( a ratio of product concentration to reactant concentration, raised to their respective stoichiometric powers).

Answer 67

Endergonic

Answer 68

Exergonic, Spontaneous, Energetically Favorable, Pushes Reactions Forward

Answer 69

Not possible to know unless you know if Temperature is a reactant or product in the reaction.

Answer 70

An adequate buffer solution should contain a weak acid and a similar (though not necessarily equal) molar amount of its conjugate base.

Answer 71

The molecules acetic acid and acetate, when present in solution in near equimolar amounts, will produce a buffer system. The pH of a buffer solution can be calculated using the Henderson Hasselbalch equation: pH = pKa + log([Base]/[Acid])

Answer 72

The pKa of an ideal buffer should be exactly at the pH that you are interested in buffering at, but pKa’s within a narrow range around the desired pH (e.g. +/- 1) are still acceptable.

Answer 73

The color change does not occur exactly at the equivalence point, it merely approximates it. The endpoint of a solution occurs where the color of the solution changes due to the weak acid/base indicator present. When choosing the indicator to use for a titration, you want to choose an indicator that changes color at a pH that is as close as possible to the pH at the equivalence point.

Answer 74

This pH must be greater than 7 Hydrofluoric acid is a weak acid, while sodium hydroxide is a strong base. Essentially, then, this question describes a weak acid/strong base titration. HF and NaOH react in a 1:1 ratio, so since the student added equimolar amounts of HF and NaOH, the two species will fully neutralize each other. The “final pH” referenced by the question stem, then, must simply be the pH at the equivalence point of a weak acid/strong base titration.

Answer 75

An adequate buffer solution should contain a weak acid and a similar (though not necessarily equal) molar amount of its conjugate base. An equal volume of 0.5 M sodium hydroxide has half the molar amount of base that 1.0 M acid does. Therefore, 0.5 M NaOH would deprotonate half the NH4+ present, resulting in 0.5 M ammonium and 0.5 M ammonia. A solution composed of 0.5 M ammonium and 0.5 ammonia would make for an appropriate buffer system.

Answer 76

Objects must share the same period, frequency and start time to be in sync

Answer 77

The frequency remains the same between mediums. The change in velocity is reflected in a change in wavelength. Since the frequency remains constant, the period also remains constant.

Answer 78

Find the wavelength by using v = f\*λ Using the wavelength, we can find the number of harmonics by using λ=(2L)/n (string + double-open ended tube) 2=(4L)/n (odd only for open end on one side of tube)

Answer 79

The **electrodes** are **made out of the same material**. The oxidation and reduction reactions are **not physically separated** in a concentration cell – they occur in the same chamber.

Answer 80

For a redox reaction reagent equation, you need to have one reduction and one oxidation reaction. You cannot have both

Answer 81

The cathode is negative in an electrolytic cell

Answer 82

If Q \> 3 under standard conditions, then E \< E°.

Answer 83

Binding energy is the amount of energy required to separate a nucleus into its individual components. A nucleus is stable because it has lower energy than its individual components. In order to break a nucleus apart into its components, you therefore need to input some amount of energy to account for this difference; this is what we call the binding energy.

Answer 84

The wavelength of an object is calculated using the equation λ = h/mv. As Planck's constant is 6.634 x 10-34, any object with a mass that is not also extremely tiny will result in a wavelength near zero. Values this small are not useful and so are rarely used to describe macroscopic objects.

Answer 85

Einstein’s experiment proceeded first with shooting high energy photons at a metal surface. Those photons then needed to contain enough energy to overcome the work function of the metal. If the work function is satisfied, any remaining energy from the incident photon was transferred to one of the metal atoms electrons, exciting it to a higher energy state. If sufficient energy was transferred to the electron, it was able to eject from the metal atom.

Answer 86

The atomic mass unit (amu) of an element listed on the periodic table of elements is representative of the weighted average of neutrons found in the various elemental isotopes + the number of protons in that element.

Answer 87

The enormous energy released from a fusion reaction is explained by the observation that the product contains lower energy nuclear components compared to the original material. In order for a fusion reaction to occur, massive amounts of energy must be used to force two atoms together into one. While this process takes a large amount of energy, it releases even more because the new atom is at a lower energy state than the original atoms added up individually. The energy released is referred to as the binding energy.

Answer 88

Gamma decay involves the emission of a gamma ray, or high-energy photon, from an excited nucleus. As a gamma ray is a photon, which is massless and has no charge, the atomic number and atomic weight of an atom does not change when it undergoes gamma decay.

Answer 89

The semi-log plot of radioactive decay transforms the exponential decay graph into a linear plot in which the y-axis is expressed logarithmically, while the x-axis remains unchanged (expressed as time).

Answer 90

The mass difference can be calculated by isolating m such that: m = E/c2

Answer 91

Electrons behave like photons of light and have both particle- and wave-like properties. The de Broglie equation gives that the wavelength of an object is equal to Planck’s constant, h, divided by the mass of the object times its velocity: λ = h/mv. By rearranging the equation, it can be found that h = λmv.

Answer 92

The work function is the minimum amount of energy required to expel an electron from an atom. Therefore, work function only determines the threshold frequency that an incident photon must equal or exceed in order to expel an electron. The work function is directly proportional to the threshold frequency: Ework function = hfthreshold. The number of photons in a light beam corresponds to its intensity, while the energy per photon corresponds to its frequency. Additionally, the threshold frequency is a property of the material determined by its work function, not a property of the light beam. Though the terms may appear similar, light frequency describes the energy per photon, while light intensity describes the number of photons in the incident light.

Answer 93

The absorption spectrum of a solution may change as a chemical reaction takes place because the **products** may **absorb different wavelengths** of light than the reactants due to differences in bonding patterns.

Answer 94

The speed of an electromagnetic wave is also called the speed of light and is dependent only on the **medium** the wave is traveling in. EM waves travel fastest in a vacuum, and slower in any other medium.

Answer 95

Speed of light decreases and frequency does not change so wavelength must decrease. We know that the frequency-wavelength relationship, c = fλ will be maintained. We also know that the **frequency does not change** as an EM wave enters a new medium: since no wave peaks are appearing out of thin air, however often a peak hits the interface from the first medium must be the same as how often peaks are passing into the second medium.. Therefore, the wavelength must change. Solving our previous equation, we can see that λ = c/f, or that wavelength is directly proportional to the speed of light in a medium. Therefore, since velocity decreased, so will the wavelength.

Answer 96

Limtations of spectrophotometry include: Very concentrated solutions might absorb too much light to give an accurate reading. The spectrophotometer must be calibrated to the wavelength the compound absorbs best. The relationship between absorbance and concentration of a sample has to be known beforehand.

Answer 97

Yes. All electromagnetic waves travel the same speed in a vacuum.

Answer 98

A preparative purification is employed when a researcher wishes to have a large amount of the desired protein, while an analytical purification is used when a researcher desires a small protein extract for qualitative analysis.

Answer 99

Step 1) Cell membranes are lysed Step 2) Proteins and other cell components are extracted Step 3) Proteins are separated by centrifugation Step 4) Unwanted proteins are precipitated out of solution Step 5) The precipitate is removed by centrifugation or filtration Step 6) Chromatography is used to isolate the protein of interest Extract proteins and other cellular components from a biological sample, usually cultured cells or from a tissue sample. Unless the proteins are secreted by the cells into the surrounding solution, this must be done by mechanically lysing the cellular membranes. Cell membranes can be lysed by repeated cycles of freezing and thawing, mechanical agitation, sonication, treatment with organic solvents, or with a detergent that disrupts the integrity of the membrane. Following cell lysis, there is an extract containing proteins, other biomolecules, membrane fragments, and various organelles. The next step is to separate proteins from other cellular components by centrifugation, which segregates particles in solution by mass, shape and density. Another technique that’s sometimes used to separate out proteins is to alter their solubility by changing the salt concentration of their surroundings. This involves adding just enough salt to just below the salt concentration at which the target protein precipitates out of solution, thus precipitating only unwanted proteins out of solution. At this point, the precipitate can be removed by centrifugation or by filtration, passing the solution through a filter to remove insoluble products. These steps alone are not very selective, however, so they are usually followed by some sort of chromatography to isolate the protein of interest.

Answer 100

In western blotting, antibodies are applied that bind directly to a specific protein. This primary antibody may itself be tagged with a dye or fluorescent marker, or more commonly, a secondary antibody that recognizes and binds to the primary antibody will be tagged in order to visualize bands corresponding to the protein of interest following gel electrophoresis.

Answer 101

Another immunochemical technique is what’s known as a radioimmunoassay, in which the concentration of protein in a sample can be assessed indirectly by measuring the extent to which the unlabeled proteins in the sample compete with radioactively labeled antigens for antibody binding sites.

Answer 102

Another important immunoassay is the enzyme-linked immunosorbent assay, or ELISA. With ELISA, the antigens in a sample are attached to a solid surface, normally on a plate. Antibodies specific to the antigen of interest are then applied to the plate, and these bind their protein antigens. After washing to remove unbound particles, the amount of bound antibody is determined by an enzymatic reaction that produces a visible signal, such as a color change, emission of fluorescence, or current that can be measured to quantify the amount of protein antigen present in the original sample. The enzymes catalyzing these reactions are linked to the antibodies.

Answer 103

Spectroscopy can also be used to quantify the amount of protein in a sample based on its absorption of light at a characteristic wavelength. In spectroscopy, light is transmitted through a sample, and the amount of light transmitted through the sample is detected by the spectrometer. This is used to produce an absorption spectrum with peaks of high absorption of light by the sample, corresponding to low transmittance of light through the sample. Protein concentration can then be calculated using the Beer-Lambert law.

Answer 104

Sound waves can be classified as: **longitudinal**, **compression** and **pressure** (waves)

Answer 105

A material with a large bulk modulus is not compressible, which means sound waves have an easier time traveling through the medium.

Answer 106

The equation for decibels is: dB = 10 log (I/I0)

Answer 107

f' = f0 (vsound - vobserver / vsound + vsource)

Answer 108

The observer is moving towards the source | positive vsource The observer is moving away from the source | negative vobserver The source is moving towards the observer | negative vsource The source is moving away from the observer | positive vsource

Answer 109

Speed, velocity and frequency are part of the Doppler equation

Answer 110

When the enol form exhibits extended conjugation more than the keto form then the enol form is will predominate. ![]()