Chem/Phys Missed Questions Flashcards
Activated fatty acids undergo beta-oxidation, 4 step process in which two carbons at a time are converted to acetyl-CoA.
How many NADH molecules will be produced from palmitoyl-CoA?
1 molecule of NADH is made for every complete cycle of B-oxidation
2 carbons are removed each cycle
palmitoyl-CoA has 16 carbons, 7 cycles, 7 NADH
What is a transferase?
transfers a specific group from one molecule to another (phosphate transfer)
What is a lyase? hydrolase? oxidoreductase?
catalyzes breaking of bonds without using water
catalyzes hydrolysis of a molecule with water
movement of electrons
Molecular geometry in increasing order.
- linear: 2 bonds
- trigonal planar: 3 bonds
- bent: 2 bonds, 1 LP
- tetrahedral: 4 bonds
- trigonal pyramidal: 3 bonds, 1 LP
- trigonal bipyramidal: 5 bonds or 4 B + 1 LP, 3 + 2
- octahedral: 6 bonds, 5/1, 4/2
How do you determine the mole fraction of O2 inhaled?
partial pressure is equivalent to mole fractions
Amount inhaled found by dividing the specific amount by the total pressure
How do you calculate Coulomb’s Law?
electrostatic force
F = kq1q2 / r^2
What is a 30 dB increase do to the magnitude of the sound?
decibels are on a log scale
increases it by 10^3
1000x greater
What is the formula of monosaccharides and disaccharides?
monosaccharides: C6H12O6
disaccharide: C12H22O11
How are peptides formed?
N terminal attacks C
amino acid with free N gets named first: N–>C
What is the potential energy of a spring?
U = (1/2) k x^2
What role does the acid play in Fischer esterification?
protonates the carbonyl oxygen, making the carbon more electrophilic and susceptible to attack
CATALYST
Characteristics of ethanoic anhydride?
highly reactive (in water, forms back into two CA), formed via dehydration, WOULD NOT form in aq solution
List the first 4 alkanes.
methane
ethane
propane
butane
How do you determine priority in R/S configuration?
highest priority groups are highest atomic number. CH3 < CH2X. R clockwise, S counterclockwise
What do salt bridges do in electrochemical cells?
prevent charge build-up in galvanic cells
- maintains the electrical neutrality by releasing spectator ions so that the redox reaction continues
What is the difference between galvanic and electrolytic cells?
galvanic: converts chemical energy into electrical energy through a spontaneous redox reaction
electrolytic: electrical energy to drive a non-spontaneous reaction
What is Gibb’s free energy equation ?
dG = dH - TdS
H: enthalpy; + endothermic
T: temp; 273K
S: entropy; randomness
G: negative is spontaneous
What affects nucleic acid annealing?
spontaneous and driven by formation of H-bonds
electrostatic interactions, histones (structure + protect DNA) negatively affects formation
How do you determine the terminals in a galvanic cell?
anode is terminal where oxidation occurs; higher oxidation potential, lower reduction potential goes here
What happens in beta+ decay?
proton into a neutron, emission of a positron and neutrino from the nucleus
drops atomic number by 1, same atomic mass
What is laminar flow through a closed system?
fluid moves smoothly in parallel layers
v1A1 = v2A2; velocity and cross sectional areas
greatest velocity occurs in region of smallest cross sectional area
What is buoyant force?
upward force exerted by a fluid on an object submerged in it
Fb = pf * V * g
- pf: density of the fluid
- V: volume of the fluid displaced by the object
- g: acceleration due to gravity
An object is submerged in a pool and sinks. Assuming H2O is an ideal fluid, what is true?
the weight (m*g) of the object is greater than the buoyant force because it is accelerating downward (g)
ideal fluids have 0 viscosity (no drag/R), so the object’s acceleration does not decrease as it hits the bottom of the pool
How is focal length related to curvature?
f = r/2
How do you figure out how much energy is liberated from transforming mass in a nuclear fission reaction?
mass defect
mass reactants - mass products = mass turned into energy * conversion factor
Where is pressure the greatest in a static, closed system?
at the lowest point
What is the best approximation of an ideal fluid?
any type of gas because it has lowest viscosity
How does Pascal’s Principle relate to the continuity equation? How does the height of the fluid factor in?
Pascal’s Principle: Pressure is transmitted equally in all directions in a confined fluid in a closed system
Continuity equation: A1v1 = A2v2 –> flow rate is constant for incompressible fluid
greater height increases pressure (P = pgh)
What is the difference between chlorate and hypochlorite?
chlorate: ClO3-
hypochlorite: ClO-
What is required to break an ester?
strong acid or base and water
What cannot be in a rate law?
anything following the rate-determining step
What is an anion exchange column used for? Why would you increase the concentration of NaCl ?
positively charged stationary phase to extract negatively charged molecules
NaCl: Cl- ions compete with the protein for binding, causing it to elute out from the column
What is the average weight of an amino acid?
110 Daltons
How is A and T related in A = log(1/T)
inversely
A tested sample absorbs light at 3 different wavelengths. Overall, the sample has higher maximum wavelengths than expected. What is the identity of the solution?
benzene: has three different sets of pi electrons that absorb at different wavelengths and the conjugation increases the wavelength expected
Rxn of aldehyde with water results in a diol. PCC does not react with aldehydes. what does this imply about PCC?
PCC is anhydrous (does not work in water)
What is a disproportionation reaction?
type of redox reaction in which an element undergoes both oxidation and reduction to form two different products
When you mix a solution of benzoic acid, phenol, and aniline (aromatic amine) in dichloromethane (p=1.33) in a separatory funnel with NaOH, what ends up in the bottom layer?
aniline: only molecule that does not react with NaOH and is not water soluble, so it will stay with dichloromethane (more dense than water and not miscible with it)
How do you determine the position of something in a chair orientation when given the ring structure?
look at the largest group; almost always equitorial
- dashed = above the plane of the ring
preserve all equitorial conformation **
What substrates are needed for the synthesis of a hemiketal?
ketone + alcohol
hemiacetal = aldehyde + alcohol
When do you use fractional vs. simple distillation?
fractional: boiling points are less than 25 degrees apart
simple: boiling points are under 150 degrees and are at least 25 degrees apart
What do solubility curves show?
temperature (x) vs. solubility (y)
-physiologic: 37
- room: 25
above the line is supersaturated, below is unsaturated
solutions with the same solubility do not necessarily have the same molarity
What is necessary for light absorbance on an IR spectrum?
vibration must result in change in the bond dipole moment
- diatomic molecules do not exhibit absorption
What will produce butanoic acid with acetone, CrO3, and aqueous H2SO4?
1-butanol because it is a primary alcohol
in a jones reaction, primary alcohols produce CA, secondary alcohols produce ketones
What solvent would promote a racemization of (R)-2-chloropentane?
heat a solution of it with lithium chloride and DMSO = polar, aprotic solvent that promotes Sn2 reactions
What is gravity filtration used for?
collect liquids from solids in an efficient way
Assuming the continuity equation applies to arteries, what is an explanation for why vascular fluttering (collapses on itself) occurs in atherosclerosis?
the initial narrowing of the blood vessel causes increase in velocity of the blood, decreasing the pressure in the arteries (Bernoulli’s equation). A large enough pressure drop would lead to its collapse
What shape is NH2R?
trigonal pyramidal: 3 bonds, 1 lone pair
linear: 2 bonds
trigonal planar: 3 bonds
tetrahedral: 4 bonds
trigonal bipyramidal: 5 bonds
octahedral: 6 bonds
When placed in an electric field, what would migrate towards the cathode at pH 7?
amino groups are protonated and positive, CA are deprotonated and negative, so need something with more amino groups (NH2)
cathode = negatively charged, amino positively charged
What is efficiency? How does accidentally calibrating weights as 3 pounds heavier than they actually are affect the efficiency in the experiment?
work output / work input
- work output: weight * distance – this would be artificially high
- work input: force needed to move the weights – this would stay the same
produces a high efficiency
percent error is more for smaller weights, skewing it more
What happens if the cross-sectional area of the ductus arteriosus decreases in neonatal lungs?
increases resistance, so blood flow decreases
When a parcel of hot gas rises, the expands adiabatically, doing work on the surrounding air, resulting in decrease temperature. Why does temperature decrease?
as the parcel expands adiabatically, it does work on the surrounding air without taking in any heat
- means the internal energy of the gas decreases (U = Q-W where Q doesn’t change)
- internal energy decreases, so does temp
How does buoyant force change with altitude when looking at two balloons of equal volume?
buoyant = weight of fluid it displaces
the atmosphere is more dense at 2000 m vs. 2600m, so the weight of air displaced by the balloons will be greater at 2000 m than 2600m
What is convection?
heat is transferred by movement of heated fluid (air or water)
What is required for aromaticity?
conjugated, planar ring = 4n + 2 pi electrons
What amino acid would exhibit strongest interaction with the stationary phase of a cation exchange column at pH of 7?
lysine
exchange columns are named for the charge of the ion that binds to the column
cation exchange: negatively charged stationary phase to attract + ions
How do you calculate the voltage of a voltaic cell?
add the reduction potentials without multiplying them by their stoich coefficients; this is an INTRINSIC property (doesn’t depend on the amount of substance involved)
can do this by subtracting the reduction potentials (cat - anode) or by reversing the sign of the thing getting oxidized
must be positive if it is driving a device
What is the specific gravity of water?
1
What is the heat energy of a resistor proportional to ?
power = I V
Describe the characteristics of an ether.
R-O-R’
less polar than alcohols, making it a relatively nonpolar aprotic solvent used for Sn2 reactions
What happens to configuration in an Sn2 reaction?
the stereochemistry is inverted ONLY at the carbon that is attacked by the nucleophile
What is the electrical and molecular geometry of XeCl4?
electrical: octahedral
molecular: square planar
What is the expected m/z peak of the molecular ion peak (M+) in mass spec?
molecular weight of everything in the compound
What is the rule for electrical conductivity?
there is no periodic trend, but
metals > metalloids > nonmetals
What are the strong acids?
HCl, HNO3, H2SO4, HBr, HI, HClO4, HClO3
For converting ring structures into chair conformations, what is important?
you need to move in the same direction as the ring when you count (counterclockwise or clockwise)
dash down, wedge up
What is the N-H stretch on IR?
3600-3200 cm-1
What is ionic bond character?
the difference in electronegativity
- increases with larger difference
further away on the periodic table increases ionic bond character
NaCl > NaBr > MgCl2 > MgBr2
What happens when sound reflects off an interface between two media?
reflection has reduced intensity because some of the sound is transmitted into the new media
- speed, wavelength, and frequency is the same
Where in a system with elastic cords is the potential energy the greatest?
when the user is using maximal effort (tension in the cord is the highest)
U = 1/2 kx^2
What is the loop and junction theorem based on?
conservation of electric charge
- current entering a junction must equal the current leaving a junction
How do you find the equilibrium constant of the reverse reaction?
1/Kc where Kc is the equilibrium constant of the forward reaction
How does the molecular weight of carboxylic acids affect boiling point?
higher molecular weight = higher boiling point
- stronger IMF (LDF)
Explain methyl ethyl propyl naming?
ane to yl when the alkane is a substituent
methane = methyl
ethane = ethyl
propane = propyl
What molecules exhibit the most rigid double bonds?
molecules without resonance structures
- electrons can’t delocalize
ex) ethene
Why can molecular mass (in amu) not be greater than molar mass (in grams)?
amu: mass of single atoms
1 amu = 1.66x10^-24 g
molar mass (g/mol) = weighted average of all possible molecular masses (single molecule, amu)
- some molecular masses will be above or below molar masses
different ways to measure the same thing: one for single molecule, the other for mole
- numerically the same
In adiabatic process, what is the change in internal energy?
U = -W
How do you find nodes and antinodes depending on the type of tube it is?
tube with both ends open
- ends are antinodes
- nodes = n
- antinodes = n + 1
- L = n lambda / 2
tube with one end opened
- closed end is node
- open end is antinode
- only odd harmonics
- 1 (1N, 1AN), 3 (2N, 2 AN), 5 (3N, 3 AN)
- L = n lambda / 4
tube with both ends closed
- both ends nodes
- nodes = n+1
- antinodes = n
- L = n lambda / 2
node = min
antinode = max
Which proton is the most acidic in a dicarboxylic acid?
the ones attached to the oxygen
What does adding salt to water do to the BP?
increase: requires greater average kinetic energy of the liquid to produce a vapor pressure equal to the external pressure
**BP = temp at which vapor pressure of solution = atmospheric pressure
What do boiling chips and vacuum distillation used for in distillations?
boiling chips: site for gas bubbles to form to prevent superheating of the solution
vacuum distillation: lowers the pressure inside the distillation flask, lowering the boiling point of the solution
A book rests on a table. The book experiences a gravitational force of mg due to Earth’s gravity. According to Newton’s third law, what is the corresponding reaction force:
the earth experiences a gravitational force of mg from the book
Fa on b = - Fb on a
What is true about diatomic nitrogen gas?
relatively inert and can be used in the lab to prevent unwanted side reactions
What bond angle between the central carbon of acetone and the other two carbons?
sp2 = 120 trigonal planar
How do the reduction potentials play into the electron transport chain?
electrons are passed from species with less positive reduction potentials to those with more positive reduction potentials
O2 is the final electron acceptor, so it must have the highest reduction potential
When delta G is negative, what is the value of K?
to be spontaneous, G = -RTln(K) has to be negative, so ln(K) must be positive, therefore K > 1 (favors products)
A ray of white light strikes the surface of water in a beaker. The index of refraction of the water is 1.33 and the angle of incidence is 30º. All of the following are true EXCEPT:
I. the angle of reflection is 30°.
II. the angle of refraction is 30°.
III. total internal reflection will result, depending on the critical angle.
II and III
angle of incidence always equals the angle of reflection (I)
light entering a more dense medium will be bent towards the normal (less than 30 degrees)
If delta H is negative, when is the reaction spontaneous?
at low temperatures when delta S is negative (entropy is decreasing)
Researchers have developed a novel enzyme that is able to catalyze the reduction of any partially oxidized nitrogen in the six-atom ring found in the structure of the adenine base pair. Which of the following changes might you expect to see in the base pairs of DNA as a consequence of the action of this enzyme?
Reduction of adenine creates the ability to form 3 or 4 instead of just two, so it would preferentially bond with cytosine (purine + pyrimidine)
What is the primary reason that ammonia is gaseous, but the ammonium ion is not?
NH4+ is charged: net positive charge allows for attraction to polar aqueous solvent, increasing BP
How do you count the number of pi-electrons in a molecule?
double bonds + lone pairs on atoms in hetero ring structures (nitrogen)
What changes the equilibrium constant?
temperature
What does an equilibrium constant close to 1 mean?
reaction does not favor either reactants or products heavily
Is the nitrogen of an amino group a better nucleophile than the oxygen of an alcohol when they are both attached to a benzene ring?
nitrogen is better nucleophile because it doesn’t hold its electron as tightly as oxygen
How does inserting a dielectric between the plates of a capacitor change the energy?
increases the capacitance
the only thing that affects voltage is the battery itself
Why can’t an electric field oriented vertically produce movement horizontally?
the equipotential lines do not have an energy gradient, so no horizontal movement happens
When do electrons in a circuit have the highest electrical potential energy?
when leaving the battery: none of the PE is lost as heat or converted into kinetic energy
In an extraction, what gets eluted first?
the most dense layer
- when specific gravity is greater than 1, that solvent with elute before the aqueous layer does
When a spring is max compressed by 30 cm with a spring constant of 100 N/m, how much kinetic energy does a 113g balloon launched by the spring have when it reaches max velocity?
at max velocity, there is 0 displacement (all PE into KE)
U = 0.5kx^2 = 4.5 J
What bonds have the smallest dipole moment?
- nonpolar covalent bonds (0)
- small difference in electronegativity (atoms close together)
- long bond lengths
What chemical properties do alkaline-earth metals have?
readily oxidized to +2, increasing reactivity with increasing atomic number, group two metals that form hydrogen gas when reacting with water
How are imines and enamines formed?
ketone + primary amine = imine
ketone + secondary amine = enamine
How does number of alkyl substituents affect carbocation and carbanion stability?
carbocation: more = better
- EDG
carbanion: more = worse
- more reactive
Ultrasonic shock wave devices may be used in medical settings to disrupt disease structures located deep in the body. The device user can control the frequency of emitted waveforms. The adjustment of waveform frequency:
enables high-amplitude resonance within diverse target tissues
- shock wave frequency approaches or is equal to the resonance frequency of the target structure
does not eliminate attenuation effects
Why does the tiled part of a floor in a room at room temperature feel colder than the carpeted part?
the thermal conductivity of the tile is higher than the thermal conductivity of the carpet, making heat transfer faster
- objects at the same temp with different thermal conductivity are perceived to be at different temperatures
When dealing with an energy conservation problem, what unit is mass in?
kg
J = kg * m^2 / s^2
Ketose vs. aldose and pyranose vs. furanose?
ketose: monosaccharide with ketone group on second carbon (fructose)
aldose: monosaccharide with an aldehyde group on first carbon (glucose)
furanose: 5 membered ring (4C, 1 O); fructose
pyranose: 6 membered ring (5C, 1O); glucose
Ketoses such as fuctose are expected to give a positive Tollens test because:
ketoses tautomerize to aldose
Tollens test: identifies presence of aldehydes and hydroxyl ketones, and uses oxidizing agent [Ag(NH3)2]+ to oxidize to CA
distinguishes aldehydes from ketones
