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CEM 141 (1) Questions & 100% Verified Correct Answers with complete solutions (Latest update
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CEM 141 (1) Questions & 100% Verified Correct Answers with complete solutions (Latest update
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CEM 141Because both the alpha particle and the nucleus are positively charged and so the alpha particle
is repelled. - ANS-Why are alpha particles deflected by the nucleus of the atom?
False - ANS-True/False: All atoms of an element are identical and have the same mass and
properties.
False; Atoms of the same element can have different numbers of neutrons. - ANS-Reasoning
for the statement "All atoms of an element are identical and have the same mass and
properties." being true/false.
The nature of the electron is independent of the material form which it emerges. - ANS-What is
the evidence that electrons are subatomic particles?
The properties of matter can be explained by understanding that matter is composed of atoms
that interact and move in various predictable ways. - ANS-Which is a theory?
Because iodine has a larger more polarizable electron cloud. - ANS-Why is the boiling point of
iodine higher than that of bromine?
The electrostatic attraction between the iodine molecules requires more energy to overcome. -
ANS-Reasoning for iodine having a higher boiling point than bromine?
When the bromine melts, attractive forces between molecules are overcome; when the bromine
forms a gas, attractive forces between molecules are overcome. - ANS-This picture is a
representation of solid bromine, Br2 (s), which exists as diatomic molecules. When Br(s) is
heated it melts (at 266K) and then becomes a gas (at 332K). What is happening?
New LDFs are formed, Energy is released to the surroundings, and energy is transferred via
collisions. - ANS-When liquid oxygen (O2) is cooled down, eventually it freezes. Which of these
best explains the forces and energy changes that take place during this process?
Both gravitational and electrostatic. - ANS-For a pencil sitting on a desk, what forces are acting
on the pencil?
The well, because the attractive and repulsive forces on the system are equal. - ANS-At very
low temperatures, at which point in this curve would a system composed of two helium atoms be
most stable?
Two protons. - ANS-The graph shows the change in potential energy as two particles approach.
Which particles are most likely to produce this change in energy?
, Thermal energy is transferred upon collision with other atoms. - ANS-How do atoms know that
the temperature is increasing?
Two masses, one of 100g and one of 1g, separated by 5 meters. - ANS-You have two systems:
1. Two masses, each of 10g, separated by 10 meters.
2. Two masses, one of 100g and one of 1g, separated by 5 meters.
Between which two objects is the gravitational force the strongest?
London Dispersion Forces. - ANS-In the solid state, atoms of xenon are held together by
The depth of the well tells you how much energy is required to break an interaction. -
ANS-Which of the following statements is true about the potential energy minimum for the
approach of two atoms?
Energy is required. - ANS-In breaking a single chemical bond:
Because there is an attractive force between the two atoms. - ANS-As two atoms approach
each other why does the potential energy decrease?
Light - ANS-Which of the following does not have atoms in it?
Neutron; it has no charge and is therefore more difficult to detect. - ANS-Which subatomic
particle was discovered LAST? Why?
3 - ANS-Ammonia reacts with carbon dioxide to produce urea and water:
2NH3 + CO2 --> (NH2)2CO + H2O
Given the initial mixture of NH3 and CO2 shown to the right, assume the reaction proceeds with
100% yield.
How many molecules of urea are produced?
1 - ANS-How many molecules of carbon dioxide remain at the end of the reaction?
8.82 g - ANS-If 5.00 grams of ammonia react with excess carbon dioxide, how many grams of
urea would be produced?
Decreases; the relative attraction between the protons and the outer electrons increases. -
ANS-Atomic radius _______ from left to right across a row on the Periodic table. Why?
Energy level diagrams describe electron behavior of all elements but the Bohr model only
describes electron behavior for hydrogen; energy level diagrams do not imply distance from the
nucleus but the Bohr model does. - ANS-Why do we sue an energy level diagram rather than
the Bohr model of the atom to describe electron behavior in atoms?
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