Chem/Phys Flashcards
(16 cards)
What is the Rf value in thin layer chromatography and what does it indicate?
The Rf value is equal to the distance traveled by the solute/distance traveled by the nonpolar solvent (usually hexane). The least polar compound would be expected to have the highest Rf value due to its high solubility in hexane.
A higher Rf value indicates the compound has traveled further than other compounds when compared to the solvent.
Ionization energy
When the ionization energy (IE) increases that means the electrons are closer to the nucleus therefore lower in energy.
Ex: if an electron is transitioning from a shell with an IE of 2 keV to a shell with an IE of 70 keV, it will emit an x-ray that is 68 keV lower in energy.
If the electron went from 70 keV to the shell with an IE of 2 keV then energy would be required for the transition b/c lower IE means higher energy state.
How do you calculate ∆G’?
∆G’ = ∆G°’ + RT ln Q
Q = [Products]/[Reactants] R = 8.31 T= 310 K
How does Newton’s Third Law apply to a sprinter running on a track?
F(track on sprinter) = F(sprinter on track)
Newton’s Third Law says that the force of object 1 on object 2 is always equal and opposite to the force of object 2 on object 1 (sometimes called “partner forces” or “action-reaction” pairs). Thus, the force of the sprinter on the track is equal in magnitude to the force of the track on the sprinter.
It doesn’t matter whether the sprinter is accelerating at the time or not.
Which value remains constant for an acid-base equilibrium?
pKa.
The acid-base equilibrium constant, Ka, is a constant for a given reaction at a given temp, and therefore the negative log of that constant (pKa) would also be constant.
Common strong acids
Strong acids dissociate completely into their ions in water, yielding one or more protons per molecule.
The 7 common strong acids are:
HCl - hydrochloric acid HNO3 - nitric acid H2SO4 - sulfuric acid HBr - hydrobromic acid HI - hydroiodic acid HClO4 - perchloric acid HClO3 - chloric acid
Common Strong Arrhenius bases
Strong bases are bases which completely dissociate in water into the cation and OH- (hydroxide ion)
LiOH - lithium hydroxide NaOH - sodium hydroxide KOH - potassium hydroxide RbOH - rubidium hydroxide CsOH - cesium hydroxide Ca(OH)2 - calcium hydroxide Sr(OH)2 - strontium hydroxide Ba(OH)2 - barium hydroxide
Lewis Bases Superbases
Superbases are Lewis bases that are Group 1 salts of carbanions, such hydrides and amides. Lewis bases tend to be even stronger than the strong Arrhenius bases because their conjugate acids are so weak.
While Arrhenius bases are used as aqueous solutions, the superbases deprotonate water, reacting with it completely. In water, none of the original anion of a superbase remains in solution.
Ethoxide ion Butyl lithium (n-BuLi) Lithium diisopropylamide (LDA) (C6H14LiN) Lithium diethylamide (LDEA) Sodium amide (NaNH2) Sodium hydride (NaH) Lithium bis(trimethylsilyl)amide, ((CH3)3Si)2NLi
Arrhenius Acid
An Arrhenius acid is a molecule that when dissolved in water will donate an H+ in solution. Simply put, a proton donor.
Trick to recognizing one is to look for the molecule that starts with an H.
The Arrhenius definition for acids and bases only refers to compounds dissolved in water.
Arrhenius Base
An Arrhenius base is a molecule that when dissolved in water will break down to yield an OH- or hydroxide in solution.
Trick to recognizing one is to look for a molecule ending in OH, but not following CHx which refers to an alcohol.
The Arrhenius definition for acids and bases only refers to compounds dissolved in water.
Bronsted-Lowry Acid
Just like an Arrhenius acid, it is a compound that breaks down to give an H+ in solution. The only difference is that the solution does not have to be water.
Bronsted-Lowry Base
The Bronsted-Lowry base refers to any atom or ion capable of accepting or bonding to a free proton in solution. So it is the proton acceptor.
Lewis Acid
A Lewis acid refers to an atom or molecule that accepts an electron pair. The atom getting attacked or accepting those electrons in the arrow mechanism is the Lewis Acid in that reaction.
Lewis Base
A Lewis base is an electron pair donor. The molecule using its electrons to attack another atom is an electron pair donor and a Lewis base.
What can be inferred about homologous enzymes?
Homologous enzymes are thought to have arisen from a common ancestor. When asked about homologous genes or proteins, look for the answers that are only about that protein itself and not about other proteins.
As homologous genes, their DNA sequences should be very similar, almost identical.
Since the DNA sequence is very similar, if not identical, the primary structure of the protein will also be very similar, if not identical. Very similar protein sequence is likely to lead to a very similar secondary and tertiary structure.
One thing that they might not share are binding partners. If you are not told that the binding partners are homologous, you can’t assume that other proteins functioning with them will be the same.
In the ETC, how many protons are pumped into the intermembrane space per molecule of NADH and per molecule of FADH2?
NADH results in the translocation of 10 protons.
FADH2 results in the translocation of 6 protons.
