MCAT Chemistry 4 Flashcards

Terms Definitions
Amino Acid
Nonane chain length
Ethane chain length
Tridecane chain length
specific rotation(alpha)
observed rotation/concentration(g/ml)Xlength(dm)
Types of Bonds
Electrostatic attraction between positive and negative ions

Sharing of electrons between atoms: the nuclei of both atoms are pulled toward the shared electrons

Weak to moderate
Electrostatic attraction between partially positive and partially negative parts of neutral molecules
van der Waals (or London forces or dispersion forces)Weakest Transient dipoles random accumulation of electrons on one side of a molecule creates a dipole moment, which may in turn induce dipoles in other molecules

Moderate to strong
Positive nuclei in a "sea" of mobile electrons
Rydberg constant
2.18 x 10^-18 J/electron
Density = mass / volume
Symbol for change in entropy
delta S
Valence Shell Electron Pair Repulsion theory, stating that the three-dimensional molecular geometry about some central atom is determined by the elctronic repulsion between its bonding and nonbonding electron pairs.
(chemistry) a substance that changes color to indicate the presence of some ion or substance
Buffers are solutions that resist changes in pH when small amounts of acid or base are added to it.

A buffer usually consists of:
a weak acid and its conjugate base or a weak base and its conjugate acid.

Such systems have the greatest buffering capability when the two components are in equal concentration.
(e.g. an acetic acid/acetate buffer has greatest buffering capability when [acetic acid] = [acetate], and therefore when
pH = pKa + log10[acetate]/[acetic acid]
= pKa + log10(1)
= pKa + 0
= pKa = 4.74)
secondary structure
describes hydrogen bonding
alpha helix and beta pleated sheets
keratin in hair
Group 7A
halogens; ns2np5,, 2nd most reactive group, The Halogens; very active because of need to fill; form -1 ions; 7 electrons in valence shell; tend to form salts with elements from groups 1A and 2A
a concentration unit of a solution expressed as moles of solute dissolved per liter of solution
Arrhenius Definition
defined acids as subtsances that produced H ions in water, while bases produced OH ions. When they reacted together, H and OH neutralise to make water
T/F Enthalpy is independent of the route of a reaction
Definitions of Acid/Base
Acid Donates proton
Base Accepts proton

Acid Donates proton
Base Donates OH- (hydroxyl) group

Acid Accepts electron pair Base Donates electron pair
limiting reactants
1)determine moles needed
2)look at eq. determine limiting reagent
Name the intermolecular forces from strongest to weakest
Ionic>dipole (h-bonds)>London dispersion forces
atomic radius
one-half of the distance between the center of identical atoms that are not bonded together. Since effective nuclear charge increases when moving from left to right each additional electron is pulled more strogly toward the nucleus.
a horizontal row of elements in the periodic table
Net ionic equation
A representation of a displacement reaction showing only the reactive species and omitting the spectator ions.
Ground state
the lowest allowable energy state of an atom
Hydrogen bonding
the intermolecular force in which a hydrogen atom that is bonded to a highly electronegative atom is attracted to an unshared pair of electrons of an electronegative atom in a nearby molecule
crystalline solid
solids in which the particles are arranged in a repeating, 3-D pattern, has a specific melting point, classified as ionic network covalent, metallic or molecular.
Effective nuclear charge
Resulting positive nuclear charge an outer electron senses after accounting for the shielding effect of inner core electrons. Abbreviated as Z(eff). Increases from left to right, and bottom to top on the Periodic Table.
What else can entropy be described as?
Unrecoverable energy
Gibb's Free Energy
Whether a chemical reaction is spontaneous (i.e. the formation of the products is favored) or not depends on two driving forces: DH and DS. Spontaneous reactions tend to occur when potential energy is released as heat through the breaking and formation of bonds (DH <0), or when the system becomes more disordered (DS >0), or both.
DG incorporates both DH and DS, as show below.
where G is Gibb's free energy (so named because it is the energy that is free to do work),
H is enthalpy (heat produced or consumed under conditions of constant pressure),
S is entropy (degree of disorder), and
T is temperature in K.
Why is DS multiplied by T? The higher the temperature, the greater the kinetic energy of the molecules and, thus, the greater the tendency for the system to go to a state of increased disorder (an analogy is the increased disorder an earthquake creates).
If DG <0, the forward reaction is spontaneous.
However, even if a reaction is spontaneous, if the activation energy is too high it will not proceed. Such a reaction is said to be under kinetic control and may require the use of a catalyst or energy input such as heat (which would also alter the equilibrium position).
If a reaction occurs as DG predicts, it is said to be under thermodynamic control.
Conversion of an element to a new element due to a change in # of protons

alpha or beta decay
Enthalpy Difference
difference in heat content btwn the products and reactants
# of gram equivelent weights in a liter of solution
What are the two parts of electrochemical reactions
oxidation and reduction
A subdivision of an energy level in an atom. They are divided into orbitals.
heisenberg uncertainty principle
states that it is impossible to determine simultaneously both the position and momentum of an electron or any other particle
periodic trends
property of the elements that can be predicted from the arrangement of the periodic table
Ion dipole interactions
When dipoles are dissolved in a solution where ions are present ions wil arrange themselves with the opposite charged end of the dipole.
theoretical yield
the maximum amount of product that can be produced from a given amount of reactant
Metathesis reactions
reactions in which none of the atoms undergoes oxidation or reduction.
Examples of metathesis reactions are:
Acid-base reactions that involve a transfer of H+,
e.g. NaOH + HCl « NaCl + H2O
Acid-base reactions that involve the sharing of a pair of electrons by a Lewis base and a Lewis acid,
e.g. Cu2+ + 4NH3 « Cu(NH3)42+
Arhenius Theory
an acid yields protons in soln. (H+)
a base yields OH-
The phase of a substance depends on two things other than intermolecular forces
Temp and Pressure
amorphous solid
A solid made up of particles that are not arranged in a regular pattern.
Common ion effect
The molar solubility of one salt is reduced when another salt, having a common ion is brought into the same solution
Bronsted Lowry
A model of acids and bases which an acid is hydrogen ion donor and base is a hydrogen ion acceptor.
What does a positive delta H indicate
reaction is endothermic (endergonic_
Relationship between Gibb's Free Energy and Keq and E (cell potential for a reaction)
An indication of the equilibrium position of a reaction is provided by each of DG, Keq, and E. DG looks at the thermodynamics of a reaction, while E looks at the relative tendencies of reactants to be oxidized or reduced. Thus they are related to each other.
Keq = e DG°/-RT
Thus if DG is large and negative, Keq will be large.
And, Keq = enFE°/RT
If E is large and positive, Keq will be large.
Also, DG° = -nFE°
Thus, if E is positive, DG will be negative.
(Note: the symbol ° denotes that standard states exist, i.e. the concentration of each reactant and product is 1 M if in solution, and 0.1 MPa if gaseous.)
Oxidation Number
The oxidation number of an atom is the charge that atom would carry if the compound it is a part of were composed of ions.
# of e- in the atom's highest # d shell
What are the three ways of producing light that lead to three different kinds of spectra?
Blackbody emmisions, spectral emmission, and charge acceleration (broad continuous spectrum, discrete spectrum and narrow continuous spectrum, respectively)
Atomic weight
The weight in grams of one mole of a given elementand is expressedin tems of grams per mole.
What does delta G indicate
the energy that is available for useful work
Coordinate Covalent Bond
when both e- in a covalent bond are supplied by one atom
Whst three things must be considered to determine if a chemical reaction will occur?
Change in enthalpy, change in entropy, and temp
Laws of Thermodynamics
3rd law:
The entropy of a pure crystal at 0 K is zero. (Thus the absolute amount of entropy of a system is measurable.)
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