mcat chem info
Which of the following elements is expected to deviate most from the predicted rw using the de Broglie wavelength correlation described above?
C
Which of the following appropriately ranks the atoms from smallest to largest atomic radius?
C < P < Al < Ge
Why do chlorine atoms form anions more easily than they form cations?
Chlorine can gain one electron in order to complete its outer shell.
Beta decay is most likely to have what effect on atomic radius?
Decreased atomic radius due to increased effective nuclear charge Beta decay involves the conversion of a neutron to a proton (with release of an electron) and an increase in effective nuclear charge.
Which of the following would have the biggest decrease in entropy for a gas in a piston cylinder?
Deposition Deposition is the process of going from a vapor to a solid, so since this phase change from the least ordered to most ordered phase is made explicit
In the formation of a bond, what dictates the distance between the two atoms?
Distance at which attractive and repulsive forces are equal Bonds will settle at a distance that is most energetically favorable
In organic solution, F- deprotonates dissolved HCl. Which of the following explains this observation?
F- has a smaller radius than Cl-.
According to the passage, which of the following would have the least impact on the measurement of atomic radius?
Gamma decay Gamma decay, involving the release of energy from an excited nucleus, would have the least impact on atomic radius.
Which of the following would have the highest energy?
Gamma rays, because they have higher frequencies than radio waves
Accurate determination of the GEW of an unknown in this experiment is most dependent on:
Having the unknown metal be the limiting reagent.
Which of the following is the most stable ionization state for Sn
Sn+2
in the ionization of titanium, which subshell will lose its electrons first and why?
The 4s subshell because it has the least stable orbitals. if a subshell has a high energy, then it is less stable,
A student performs Millikan's experiment and is able to suspend an oil drop with no velocity. The mass of the oil drop is known, and the electric field strength required to suspend it is recorded. If Equations 2 and 3 are used to solve for the magnitude of charge on an electron, what is the most likely result?
The calculated charge will be overestimated because buoyancy is not considered.
An atom of beryllium is repelled by an externally produced magnetic field. Which of the following explains this phenomenon?
The electrons of beryllium are all spin-paired and the atom is diamagnetic.
Which of the following is true about the amount of shielding the highest energy electrons of calcium and arsenic experience?
The electrons of calcium have a lesser amount of shielding than the electrons of arsenic. the amount of shielding that the highest energy electrons of an atom feels is determined by the number of filled shells in that atom (inner core electrons), as well as subshells within an energy level
Consider the following reaction: CH4 + 2 O2 → CO2 + 2 H2O ΔH° = -860 kJ What is the best explanation for why the reaction is exothermic?
The energy required to break reactant bonds is less than the energy released when product bonds are formed.
Later experiments observes an rw for hydrogen of 1.1 Å. What is a possible reason for obtaining this particular value
The hydrogen atom was bound to a halide rather than another hydrogen
The reactivity of alkali metals follows the trend Cs > Rb > K > Na > Li. Which of the following is the best explanation for this trend?
The ionization energy increases from Cs to Li.
In a subsequent experiment, the student found that a particular element failed to give reproducible results. After four attempts, the element's GEW varied by over 25%. Which one of the following statements best explains this outcome?
The metal was a transition metal that had multiple permitted oxidation states.
Which of the following ions will align itself parallel to the poles of a magnetic field?
V3+ Any atom or ion that aligns itself parallel to a magnetic field is defined as paramagnetic, and all such species have unpaired electrons in their orbitals.
Does a small atomic radius correspond to a high ionization energy?
Yes, because the shorter distance between the positive nucleus and the negative electron enhances electrostatic attraction, and thus makes it difficult for these electrons to be removed.
Give the electronic configuration of vanadium, V.
[Ar] 4s23d3
diamagnetic
all electrons are paired
electronegativity increases as you move from the
bottom left to the top right of the periodic table. F > O > N > Cl > Br > I > S > C ≈ H.
Since the electron is moving closer to the nucleus, a photon will be
emitted Hydrogen has only one electron, so if it is in the second energy level it must be in an excited state. The electron will therefore transition from a high energy level to a lower one,
The first law of thermodynamics stipulates that
energy is always conserved
A sample of excited hydrogen atoms emits a light spectrum of specific, characteristic wavelengths. The light spectrum is a result of:
excited electrons dropping to lower energy levels.
Compared to carbon, nitrogen has a:
greater ionization energy and more negative electron affinity.
Compared to the electronegativity of iodine, the electronegativity of chlorine is:
greater, because decreased nuclear shielding allows for a stronger pull on the valence electrons.
Phosphate is a negatively charged
hydrophilic ion.
a photon is directly proportional to
its frequency and inversely proportional to its wavelength
Compared to the atomic radius of S, the atomic radius of Al is:
larger, due to decreased nuclear charge.
Of the following valence shell electron configurations, which is associated with the greatest stability for an atom?
ns2np6 octet
Compared to the atomic radius of calcium, the atomic radius of gallium is:
smaller, because increased nuclear charge causes electrons to be held more tightly.
the third law of thermodynamics states
that a perfect crystal possesses no entropy at absolute zero
The second law of thermodynamics states
that all processes proceed toward disorder , entropy increases
What would be the effect upon the calculated GEW of the unknown metal relative to its true GEW if the reagent sulfur contained an inert, nonvolatile impurity?
the calculated GEW would be too low. If the recorded mass of sulfur was anomalously high, and the impurity did not react with the metal, then the computed metal GEW would be too low, as it would be seen as having a lower stoichiometry with sulfur.
The zeroth law of thermodynamics states that
two systems at equilibrium with a third are in equilibrium with each other
paramagnetic
unpaired electrons
Which of the following explains the relationship between distance and ionization energy for a particular electron density?
Io is inversely proportional to the square of r; increased first ionization energy correlates with a smaller distance
Which of the following is true of ionization energy?
It decreases with period, and the second ionization energy is greater than the first.
Which of the following is true of an electron in an excited state?
It has absorbed a photon, and its energy has increased.
An intern in a laboratory is asked to clean up after a new graduate student in the lab who was making a HEPES buffered solution. The intern finds a white solid powder left on the counter from the buffer preparation and is uncertain how to dispose of it. Which of the following is the most likely identity of this white powder?
NaC3H5O3 the intern was disposing of a white powder (solid), thus we are looking for the compound that will have the strongest intermolecular forces
What is the reactivity, as indicated by the tendency to lose an electron, of sodium compared to potassium?
Potassium has a higher reactivity because the valence electron on potassium is farther from the nucleus. Reactivity of metallic elements increases down a column of the periodic table. This increase in reactivity corresponds with increased shielding from inner electron shells, increased atomic radius, and decreased ionization energy. Thus, electrons are easier to remove in potassium versus sodium.
Rank the following elements and ions from least to greatest atomic radius: S, S+, P, P-, P2-
S+ < S < P < P- < P2- Anions will have a larger radius than nuetral atoms or cations of the same, or similarly sized elements.
