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Chemistry 2005 fall final review


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Which of the following statements is not con-
sistent with the kinetic molecular theory?

1. Gases consist of a large number of parti-
cles in rapid random motion.
2. Collisions between molecules of gas are
The average velocity of molecules of two different gases is the same at the same temperature.
Based on the types and strengths of intermolecular forces present, place the compounds
C2H6; CH4; H2O; SO2; MgO
in order from lowest to highest boiling point.
CH4, C2H6, SO2, H2O, MgO
A gaseous mixture made from 6.00 grams of oxygen gas and 9.00 grams of chlorine gas is placed in a 15.0 L vessel at 10.0 degrees Celsius.
What is the total pressure in the vessel?
0.488 atm
The empirical formula of a gas is CH3O.
If 2.77 g of the gas occupies 1.00 L at exactly
0 degree C at a pressure of 760 Torr, what is the
molecular formula of the gas?
Which van der Waals coefficient dictates attractive force?
N2 has a bond order of 3 and O2 has a bond
order of 2. Based on this information, choose
the response that best completes the following
sentence, in the order listed.
N2 is (less, more) stable than O2, and has
a (larger, shorter)
more; shorter; higher
What volume is occupied by 1.00 kg of helium
at 5.00 degrees C at a pressure of 735 Torr?
5.9 E3 L
If the interaction between two species is proportional to 1/r2 , which of the following is likely
Na+ and H2O
What is the bond order of O2+
2 ?
Consider the reaction
4KO2(s) + 2CO2(g) =>
2K2CO3(s) + 3O2(g) :
How much oxygen is produced at STP if 10.5 moles of carbon dioxide are used at STP?
353 L
Rank the gas molecules CO2, C2H6, H2O, He,
H2 in terms of increasing rate of effusion.
CO2;C2H6;H2O; He;H2
If the average speed of a carbon dioxide molecule is 410 m/s at 25 degrees C, what is the average speed of a molecule of methane at the same temperature?
680 m/s
At STP, 0.500 L of fluorine gas will have a mass of
0.848 g
Which intermolecular force do all molecules possess?
dispersion forces - Dispersion forces are caused by a temporary disruption of the electron cloud. Since all molecules possess an electron cloud, all molecules possess dispersion forces.
What is the strongest evidence for hydrogen bonding?
The boiling points of NH3, H2O, and HF are abnormally high compared with the rest of the hydrides in their respective periods.
If a sample of gas is heated from 100 degrees C to
300 degrees C at constant pressure, the volume will
___ by a factor of ___.
increase; about 1.5
A(n) 3.9 L sample of gas at STP is cooled to -55 degrees C at 808 mm Hg pressure.
What is the new volume?
2.9 L
What is the density of helium gas at 750 kPa
and 25 degrees C?
1.21 g/L
For which of the following elements would the
size of the neutral atom (atomic radius) be
1. Ca
2. Na
3. K
4. Rb
5. Sr
Rb : Atomic radii become larger as you move from right to left across a row, and also larger as you move down a column. Diagonal relationships can be tricky, especially when you have to decide which of the two relationships will be the most important. Here, luckily, the comparion works well. With each successive member of a column, you are introducing a new energy level, farther and farther from the nucleus. The largest radius here would then belong to the element which sits closest to the
bottom left corner of the periodic table, which
is Rb in this example.
This is a case in which P desires to be surrounded by ten electrons. The polyatomic ion PCl4- has ____electronic geometry and ____molecular geometry.
trigonal bipyramidal; seesaw
The PF5 molecule exists, whereas NF5 does not.
Which one of the following is the BEST explanation for this fact?
1. The first five ionization energies of nitrogen are too high, but those of phosphorus are not.
2. Phosphorus can use d orbit
Phosphorus can use d orbitals in bonding, whereas nitrogen cannot.
Draw the Lewis structure for the following hydrocarbon molecule. The carbons are numbered one to four starting with the far left carbon as one.
What is the molecular shape of carbon 4?
What is the hybridization of carbon 2?
What are the bond angles of carbon 1?
120 degrees
Carbon 3 has:
3 sigma bonds and 1 pi bond.
Which of the following is polar?
1. XeF4
2. PCl5
3. ICl4-
4. SF6
5. IF5
IO3- has (3, 4, 5) regions of high electron
density and (3, 4, 5, 6, 8) bonded electrons.
4; 6
N = 8 £ 4 = 32
A = 1 + 7 + 6 + 6 + 6 = 26
S = 32 - 26 = 6
This molecule has 6 bonding electrons and one lone pair. This gives 4 regions of HED.
CCl4 is more/less polar than CHCl3 because
less: the four polar C-Cl bonds are symmetrical and cancel the dipole moments.
The ions Na+, F-, and O2- each have ten electrons. What would be the order of the sizes of these three ions?
Na+ is smaller than F- which is smaller than O2-.
Positive ions tend to be smaller than nega-
tive ions because they have fewer electrons
and the remaining electrons experience a
larger e®ective nuclear charge. Negative ions,
on the other hand, have extra electrons, each
of which experiences a lower e®ective nuclear
charge. The more extra electrons an ion has,
the larger it will be within a row, and the
more electrons an ion loses, the smaller the
ion within a row. Atomic radii and ionic
radii both increase as you move down a col-
umn since the electrons are in higher energy orbitals and further away from the nucleus.
Which of the following statements is true?
1. The electronegativity of an atom is defined as
1/2(Electron Affinity) of the atom.
2. Atoms with low ionization energies and low electron a±nities have low electronegativities.
3. The el
Atoms with low ionization energies and
low electron a±nities have low electronegativ-
Which of the following does NOT exhibit resonance?
1. CO3 2-
2. SO3
3. NO3-
4. SO3 2-
5. All of the other answers have ions or molecules which exhibit resonance.
SO3 2-
A molecule has six areas of high electron density around the central atom and has two lone pairs on the central atom.
What is the molecular geometry of this molecule?
square planar
What is the molecular shape of PCl3?
What bond angles are expected in PCl3?
109.5 degrees
The first ionization potential of the elements B, C, and N (atomic numbers 5, 6, and 7) steadily increases, but that of O is less than that of N. The best interpretation of the lower value for O is that
the half-¯lled set of p orbitals in N makes
it more di±cult to remove an electron from N
than from O.
The ionization potential is a measure of the
ease with which electrons are lost by an atom.
The ionization potential increases from left to
right across the table. The outer electronic
configuration of N atom is 2s22p3 (half-filled
orbital), which gives it extra stability. This
increases the amount of energy needed to remove the first electron from N as compared to
Write the electron con¯guration for Mo.
[Kr] 5s1 4d5
A neutral atom has a ground state electronic
configuration designated 1s2 2s2 2p2.
Which of the following statements concerning this atom is/are true?
1. All are true.
2. The atom contains 6 protons.
3. The element has atomic nu
All are true.
For n = 3 and l = 1, what is ml ?
-1, 0, +1
What is the wavelength of an electron traveling one tenth the speed of light? The speed of light is 3E8 m/s. The mass of an electron is 9.11E-28 g. Planck's constant is 6.626 E-34 J/s = 6:626 E-34 kgm2/s.
2.42 E-11 m
A neutral isolated atom has a ground state
configuration of 1s2 2s2 2p6 3s2 3p6 4s2 3d7.
Identify the element.
cobalt (Co)
Which of the following provided evidence that
the electrons in atoms are arranged in distinct energy levels?
1. the deflection of ions in a mass spectrometer
2. the observation of line spectra from gas discharge tubes
3. the scatteri
the observation of line spectra from gas discharge tubes
What is the wavelength of radiation of frequency 4.80E13 1/s?
6.25 E-6 m
Which statement concerning the electrons surrounding the nucleus of an atom is NOT
1. The number of electrons in an isolated neutral atom is equal to the atomic number.
2. The attraction of the electrons by the
nucleus helps
The second main energy level can have any number of electrons up to ten.
what is the correct order of decreasing frequency of the electromagnetic spectrum?
ultraviolet radiation, visible light, infrared radiation, radio waves
How much energy does a photon with a wavelength of 1050 nm have?
1.89 E -19 J
The Heisenberg Uncertainty Principle states that
you cannot measure exactly and simultaneously both the position and momentum (energy) of an electron.
The quantum mechanical approach to atomic structure permits the calculation of
a region about the nucleus in which an electron of specified energy will probably be found.
the photoelectric effect provided strong evidence for:
the particle nature of light

When electromagnetic radiation (light) of
su±cient minimum energy strikes a metal
cathode, electrons are knocked o® its sur-
face, travel to an anode, and form a current
through a circuit.
Two important observations were:
1) Electrons can be ejected only if the light
is su±ciently energetic. Electron ejection is
independent of time or intensity. The mini-
mum energy varies by element.
2) The current increases with increasing
intensity and is independent of color.
Therefore, light is made up of photons, each
having a particular amount of energy that can
be transferred to an electron during a colli-
sion. If the energy is equal to or greater than
the amount needed to liberate the electron, it
can escape to join the photoelectric current.
Intensity is the number of photons hitting a surface per unit time.
What is the designation for electrons in an orbital with the quantum numbers n=5 and l=2.
The element whose neutral atoms have three
half-filled 3p orbitals in the ground state configuration is
Consider the statments
Z1) When an electron falls to a lower energy level in an atom it emits electromagnetic radiation.
Z2) The energy of electromagnetic radiation
is directly proportional to its frequency.
Z3) The product of wavelen
Z1 & Z2 only
A lawyer who received a speeding ticket ar-
gues that because of the Heisenberg Uncer-
tainty Principle the radar reading is uncer-
tain. The judge, who happens to have a
science degree, rules against the lawyer.
Which of the fol
The judge is correct because the car is so massive that the uncertainty in speed is very small
What is the expected ground state electron
configuration for Tl3+?
[Xe] 4f14 5d10
The three quantum numbers for an electron in
a hydrogen atom in a certain state are n = 4, l= 2, ml= 1.
The electron is located in what type of orbital?
In the order of occupancy of electronic energy levels, the level occupied after 3d is
A liquid freezes. This process is:
an exothermic phase change
Which answer best accounts for the Cl- ions
present in the NaCl unit cell?
(1/8)*8 corner atoms + (1/2)*6 face atoms
The molar heat of fusion of water is 6.02 kJ/mol.
Calculate the energy required to melt 46.8 g
of water.
15.7 kj

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