Select the correct description for O2 and O3. These two substances are:
elements, molecules, and isotopes
compounds, molecules, and isotopes
elements, molecules, and allotropes
compounds, molecules, and allotropes
molecules, allotropes, and isotopes
What key physical property was determined in Thomson's cathode ray experiment?
the charge of a proton
the mass-to-charge ratio of a proton
the mass of an electron
the mass-to-charge ratio of an electron
the spin of an electron
If an electron moves closer to a nucleus, which of the following is true regarding the electron energy and its chemical reactivity:
its energy increases and it become more reactive
its energy increases and it becomes less reactive
its energy decreases and it becomes more reactive
its energy decreases and it becomes less reactive
According to the Bohr model for a 1-electron atomic species ( where Z = atomic number, and n = principal quantum number) , the energy of the electron in the nth orbit is proportional to:
-Z^2 / n^2
-n / Z^2
-n / Z
-n^2 / Z^2
-Z^2 / n
Compared to the photon that would be emitted as a result of the n = 2 --> n = 1 electron transition in the hydrogen atom, would the photon emitted in the 2-->1 transition of the Li^2+ ion be of lower or higher energy?
lower
higher
Select the one process involving particle interactions that would result in a decreases in energy?
Two helium atoms move farther apart
A lithium ion moves farther away from a chloride ion
An electron moves from the n=1 level to the n = 2 level
an electron moves farther away from a nucleus
Two anions move farther apart
In diagrams of p orbitals, what is the significance of the difference colors or shadings given to the two lobes?
Each lobe holds a different electron
The sign of the orbital wave function is positive in one lobe, negative in the other
The spin quantum number is +1/2 in one lobe, -1/2 in the other
The magnetic quantum number +1 in one lobe, -1 in the other
One lobe carried negative charge whereas the other lobe carries positive charge,
Which two quantum numbers are predictive of the energy of an electron in an orbital
ml and ms
n and ml
l and ml
l and ms
n and l
Which electron quantum number (QN) gives rises to the magnetic properties of atoms?
principal QN (n)
spin QN (ms)
angular momentum QN (l)
magnetic QN (ml)
Identify the main cause of the deceases in size as one moves across the row from left-to-right in the Periodic Table for relative atom sizes.
The atomic mass is increasing
The effective nuclear charge is increasing
Electron shielding is increasing
The number of electrons is increasing
The l quantum number is increasing
The following statements pertaining to electronegativity are all true except for one. Identify the one false statement.
Elements with lower energy valence orbitals have higher electronegativity
Metals are, in general, more electronegative than non mentals
Fluorine is the most electronegative element
Elements of high electronegativity are typically difficult to ionize
Electronegativity is a measure of how strongly an atom attracts bonding electrons
In general, how do non-metals compare to metals with regard to electronegativity and ionization energy? Non-metallic elements:
have higher electronegativities and are easier to ionize
have higher electronegativities and are more difficult to ionize
have lower electronegativities and are easier to ionize
have lower electronegativities and are more difficult to ionize
According to Valence Bond Theory, hybrid orbitals can be occupied by electrons that are found in:
pi bonds and lone pairs
sigma bonds only
sigma bonds, pi bonds, and lone pairs
sigma bonds and lone pairs
sigma bonds and pi bonds
All statements are true except for one. Identify the false statement.
pi bonds have no electron density on the internuclear axis
all covalent bonds contain one and only one sigma bond
when two atoms bond to form a diatomic molecule, the potential energy decreases
it is possible to form a sigma bond from two p atomic orbitals
pi bonds can be formed using ether s or p atomic orbitals
Graphite and diamond are two well-known allotropes of carbon. What is the hybridization of the carbon atom ins in each of these solids?
graphite - sp^3 diamond - sp^2
graphite - sp^2 diamond - sp
graphite - sp diamond - sp^3
graphite - sp^3 diamond - sp
graphite - sp^2 diamond - sp^3
The chemical composition of zeolites and clays is composed primarily of which three elements?
C, Fe, O
Si, Fe, O
Al, Ca, O
Al, Si, O
Mg, Si, O
For a specific substance, which one of the following process would result in the largest release of energy per mole?
evaporation
condensation
sublimation
melting
freezing
In the band theory for solid materials, Fermi level is the term that denotes the electron energy level corresponding to:
the highest occupied orbital
the lowest occupied orbital
the midpoint of the valence band
the midpoint of the conduction band
Which of the following conditions is always true for an extensive reaction? (CAUTION: carefully consider all choices before selecting an answer because certain conditions may be true for some reactions but not for all reactions.)
The value of ∆H° < 0
The value of ∆H° > 0
The value of ∆G° < 0
The value of ∆G° > 0
The value of ∆S° > 0
How does a catalyst affect the energetics of a reaction to increase the rate at which the reaction occurs?
by decreasing the free energy of the products
by decreasing the enthalpy of the products
by decreasing the activation energy
by increasing the collision frequency
by increasing the equilibrium constant
When a reaction attains equilibrium, identify the condition that must be satisfied. K s the equilibrium constant , and v is the reaction rate.
K = 0
K = 1
∆G = 0
∆G° = 0
v(forward) = v(reverse) = 0
If a chemical system consists of gas phrase molecules, which modes of motional freedom are available for dissipating heat transferred to the system from the surroundings?
rotational only
vibration only
rotation and translation
vibration and translation
translation, rotation, and vibration
Which of the following properties is not a thermodynamic state function?
heat
enthalpy
entropy
free energy
temperature
According to the Second Law of Thermodynamics, a reaction that occurs spontaneously will result in:
no change in the energy of the universe
a decrease in the energy of the system
an increase in the entropy of the universe
an increase in the entropy of the system
a decrease in the entropy of the universe
Of the following five factors, indicate all that can affect the rate of a reaction? Temperature, concentration of reactants, orientation of reactants at collision, activation energy, catalyst
temperature, concentration
temperature, activation energy
concentration, orientation, activation energy
activation energy, catalyst
all five of them
Hydrocarbons, for example, octane(C8H18), are insoluble in water, a phenomenon that is referred to as the hydrophobic effect. Thermodynamically, the standard free energy change for the reaction C8H18(l) <-> C8H18(aq) is extremely unfavorable (∆G° >> 0). Why does such a large increase in Gibbs free energy result when an octane molecule enters an aqueous phase?
the dispersion force interaction between water molecules and octane molecules is repulsive
a decrease in entropy occurs because water molecules around the octane molecule become more ordered ( with respect to bulk water)
a decrease in entropy occurs because water molecules around the octane molecule become more disordered ( with respect to bulk water)
an increase in enthaply occurs due to strong hydrogen bonding between octane molecules and water moelcules
an increase in enthaply occurs due to strong hydrogen bonding between octane molecules
Consider the three conceptual steps that we discussed for dissolving a molecular solid into a liquid solvent: (I) breaking intermolecular interactions that hold the solute molecules together in the solid (II) creating solvent cavities by breaking intermolecular interactions in the solvent (III) solute particles entering into the solvent cavities
Which of these processes are endothermic?
I only
II only
III only
I and II
II and III
Identify the role of a reducatant ( reducing agent ) and the kind of valence orbital that gives rise to strong reductants?
electron acceptor; low energy unfilled valence orbitals
electron acceptor; high energy unfilled valence orbitals
electron donor; low energy occupied valence orbitals
electron donor; high energy occupied valence orbitals
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