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Cem 141 mock exams Questions & 100% Verified Correct Answers with complete solutions (Latest update

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Cem 141 mock exams Questions & 100% Verified Correct Answers with complete solutions (Latest update

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  • August 15, 2024
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  • 2024/2025
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Cem 141 mock exams
A. I, III - ANS-Thomson's experiment allowed him to make the claim that all atoms have a sub
structure and contain smaller particles (electrons) embedded in the structure of the atom. What
evidence and reasoning allowed him to make this claim?

Evidence:
I. Electrons were ejected from the cathode, regardless of what metal the cathode was made of.
II. Electrons were bent by magnetic and electric fields

Reasoning:
III. Since the particles are emitted regardless of the nature of the cathode, they must be part of
the sub-structure of the atom
IV. Electrons must be negatively charged because they accelerate towards the anode (positive
end of the apparatus).

A. all are true - ANS-Which of these statements are true:

I. All neutral atoms and molecules attract each other.
II. London dispersion forces increase as the size of the electron cloud increases.
III. It takes energy to overcome the attractions between particles.
IV. Energy is released to the surroundings when atoms attract each other.

A - ANS-What is the claim?
A. The atom is mostly empty space with a very small dense nucleus.
B. The atom is made of positively charged matter with electrons embedded in it.

B - ANS-What is the evidence?
A. The alpha particles were deflected by the magnetic and electric fields in the apparatus.
B. Most alpha particles went straight through, only a few were deflected.

A - ANS-What is the reasoning?
A. The positively charged alpha particles were deflected by the repulsive interaction with the
positive nucleus; since only a few were deflected the nucleus must take up a very small volume
of the atom.
B. When the alpha particles get near the nucleus they are attracted by the strong nuclear force
which alters their trajectory.

B - ANS-The atomic theory of matter is an example of a scientific theory. What distinguishes it
from a scientific law such as the law of gravity? The atomic theory:

A. describes a single phenomenon.

, B. explains the underlying cause of a range of phenomena.
C. can be used to predict.
D. must be revised if evidence arises that contradicts it

D - ANS-Which is smallest?

A. an atom B. a cell C. a proton D. an electron

A - ANS-The distance between the two helium atoms where the system would be the most
stable is:

A. Where the potential energy is at a minimum.
B. Where the kinetic energy is at a minimum.
C. Where the KE and PE are equal.
D. Where the PE is as high as possible.

C - ANS-Two atoms approach and get close enough so that their electron clouds overlap. Why
does the potential energy increase?

A. This is an isolated system.
B. The kinetic energy decreases.
C. The electron clouds repel each other.
D. The London dispersion forces are very strong

C - ANS-What is the cause of the attractive force between the two He atoms?

A. London dispersion forces.
B. He atoms have a permanent dipole so that the negative end of one atom is attracted to the
positive end of the other atom.
C. The electron clouds of the He atoms may fluctuate randomly causing a transient dipole that
induces a dipole in other atoms which causes them to attract each other.
D. One He becomes positively charged and the other He atom becomes negatively charged so
they attract each other.

D - ANS-Is this statement (one of Dalton's atomic theory tenets) true or false and why?
Elements are composed of small indivisible, indestructible particles called atoms.
I. True
II. False

Reasoning
III. Atoms can neither be created nor destroyed
IV. Atoms have a sub-structure
V. Elements can be identified by the type of atoms they have in them

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