AAMC QP Chemistry Flashcards
what does the formation of a hydrogen bond require
The formation of a hydrogen bond requires both a hydrogen bond donor: a molecule with a hydrogen bonded to a highly electronegative atom such as oxygen or nitrogen, and a hydrogen bond acceptor: an electronegative atom (such as O or N) with an available lone pair of electrons.
What conditions improve or worsen the degree of separation in a distillation experiment?
- fractionating column is shortened
- creating w lower pressure in the distilling apparatus
If the fractionating column is shortened, the liquids will vaporize and condense fewer times (i.e., there will be fewer theoretical plates) and the degree of separation will WORSEN.
Creating a lower pressure inside the distilling apparatus will lower the boiling points of both liquids and narrow their difference in boiling point, making it necessary to also increase the length of the fractionating column in order to achieve the same degree of separation as obtained originally. If the length is not increased, then the degree of separation will worsen.
What conditions improve or worsen the degree of separation in a distillation experiment?
- cooling the condenser
- heating the distillation flask
Cooling the condenser with ice water will have no effect on the degree of separation because condensation takes place after the separation has occurred.
Heating the distillation flask (i.e., increasing the temperature) at a slower rate will allow both liquids more time in the fractionating column (increase the number of theoretical plates, allowing liquid and vapor to equilibrate).
when does an ionic bond form
An ionic bond is most likely to form between elements of very high and very low electronegativity.
In practice this generally means elements at the far right and far left of the periodic table respectively.
which is a better leaving group
- hydroxide
- hydroxyl
Hydroxide ion is one of the worst leaving groups in substitution reactions.
Under acidic conditions, the hydroxyl group is protonated such that the leaving group is now water, a superior leaving group, rather than hydroxide ion.
how do you calculate the number possible peptides that contain one each of n amino acids
n! (n factorial)
For n = 3 (a tripeptide), n! = 3! = 3 × 2 × 1 = 6
fatty acid formula
fatty acid salt formula
A fatty acid would have the general formula Rn—CO2H.
The corresponding fatty acid salt would have the general formula Rn—CO2– Na+.
how does an acid differ from its conjugate base (and vice versa)
An acid differs from its conjugate base only by the presence of an additional H+.
A base differs from its conjugate acid only in the lack of a single H+.
define the following:
- decomposition
- combination
- displacement
decomposition: substance undergoes a reaction to form two or more other substances
combination: two or more substances come together to form one new molecule
displacement: an element reacts with a compound, displacing an element from it
what does ionization constant mean
how likely the molecule will dissociate in solution
the higher the constant, the more likely it will dissociate in water
what happens in a redox reaction
In an oxidation-reduction reaction, the reducing agent donates electrons and is thus oxidized.
vs. the oxidizing agent accepts electrons and is thus reduced.
when is energy emitted, according to the Bohr model?
energy is emitted only when an electron falls from a higher to a lower energy level
when does a precipitate form? explain in terms of Ksp
The amount of a substance that will dissolve in water is described by the Ksp. The Ksp for a substance, AaBb, equals [A]a[B]b.
If the amount of the compound present is in excess of the Ksp, then a precipitate would form to maintain the Ksp.
groupings of the periodic table
- s/p/d/f
- nonmetals
- metalloids
- main group metals
- transition metals
see photo on phone
(1) til perfect
where does reduction vs oxidation occur
Reduction occurs at the cathode; oxidation occurs at the anode.
