CEM 141 PRACTICE EXAM QUESTIONS
WITH 100% CORRECT ANSWERS
What is the wavelength of light that has a frequency of 3.0 GHz (3* 10^6 Hz)?
A. 100 m
B. 100 nm
C. 10 cm
D. 3.0 * 10^8 m - Answer- A
What wavelength of light would break a O=O bond (it takes 8.3*10^-19 J to break one
bond)?
A. 240 nm
B. 1.5*10^-15 m
C. 500 nm
D. 10 nm - Answer- A
Atomic absorption spectra are caused by:
A. Photons moving between energy levels in an atom.
B. Electrons moving to lower energy levels and releasing photons of energy equal to the
energy difference between the levels.
C. Electrons moving to higher energy levels and absorbing photons of energy equal to
the energy difference between the levels.
D. Electrons being ejected from the surface of the metal when hit by a photon. -
Answer- C
How many core and valence electrons does carbon have?
A. 6 core, 6 valence
B. 2 core, 4 valence
C. 4 core, 2 valence
D. 10 core, 2 valence - Answer- B
What is the electron configuration of Se?
A. [Ar] 4s2 3d10 4p4
B. [Kr] 4s2 3d10 4p4
C. [Kr] 4s2 4d10 4p4
D. [Ar] 3s2 3d10 3p4 - Answer- A
What is the best explanation for a pattern such as those obtained when x-rays are
diffracted by crystals?
A. The photons and the anti-photons cancel each other out.
, B. The waves of electromagnetic radiation arrive in-phase and out of phase at the
detector.
C. The x-rays eject electrons which interfere with each other.
D. As the beam x-rays arrives the peaks give a bright spot and trough give a dark spot
on the detector. - Answer- B
What is the coefficient in front of O2?
C6H14 + O2 -> CO2 + H2O
A. 2
B. 7
C. 19
D. 32 - Answer- C
Which color represents the transition from n=2 to n=1?
A. green
B. yellow - Answer- B
How much energy is required to move from n=1 to n=2?
n=1: -13.60
n=2: -3.40
A. 13.6 eV
B. 3.4 eV
C. 10.2 eV
D. 1.51 eV - Answer- C
Which has a larger atomic radius? Mg or Ar? Why?
A. Mg, because it is a metal.
B. Mg, because its valence electrons are not as strongly attracted towards the nucleus
as those in Ar.
C. Ar, because it is a heavier element.
D. Ar, because it has more electrons and they repel each other. - Answer- B
Out of Na+, Mg2+, Ne, and F- which has the smallest radius?
A. Na+
B. Mg2+
C. Ne
D. F- - Answer- B
When and where were the carbon and oxygen atoms in your body created?
A. In plants as they were growing
B. During the big bang
C. Within stars and stellar explosions
D. During the course of digesting your food - Answer- C
Iodine and silicone dioxide are both solid at room temperature. Which has a higher
melting point and why?
WITH 100% CORRECT ANSWERS
What is the wavelength of light that has a frequency of 3.0 GHz (3* 10^6 Hz)?
A. 100 m
B. 100 nm
C. 10 cm
D. 3.0 * 10^8 m - Answer- A
What wavelength of light would break a O=O bond (it takes 8.3*10^-19 J to break one
bond)?
A. 240 nm
B. 1.5*10^-15 m
C. 500 nm
D. 10 nm - Answer- A
Atomic absorption spectra are caused by:
A. Photons moving between energy levels in an atom.
B. Electrons moving to lower energy levels and releasing photons of energy equal to the
energy difference between the levels.
C. Electrons moving to higher energy levels and absorbing photons of energy equal to
the energy difference between the levels.
D. Electrons being ejected from the surface of the metal when hit by a photon. -
Answer- C
How many core and valence electrons does carbon have?
A. 6 core, 6 valence
B. 2 core, 4 valence
C. 4 core, 2 valence
D. 10 core, 2 valence - Answer- B
What is the electron configuration of Se?
A. [Ar] 4s2 3d10 4p4
B. [Kr] 4s2 3d10 4p4
C. [Kr] 4s2 4d10 4p4
D. [Ar] 3s2 3d10 3p4 - Answer- A
What is the best explanation for a pattern such as those obtained when x-rays are
diffracted by crystals?
A. The photons and the anti-photons cancel each other out.
, B. The waves of electromagnetic radiation arrive in-phase and out of phase at the
detector.
C. The x-rays eject electrons which interfere with each other.
D. As the beam x-rays arrives the peaks give a bright spot and trough give a dark spot
on the detector. - Answer- B
What is the coefficient in front of O2?
C6H14 + O2 -> CO2 + H2O
A. 2
B. 7
C. 19
D. 32 - Answer- C
Which color represents the transition from n=2 to n=1?
A. green
B. yellow - Answer- B
How much energy is required to move from n=1 to n=2?
n=1: -13.60
n=2: -3.40
A. 13.6 eV
B. 3.4 eV
C. 10.2 eV
D. 1.51 eV - Answer- C
Which has a larger atomic radius? Mg or Ar? Why?
A. Mg, because it is a metal.
B. Mg, because its valence electrons are not as strongly attracted towards the nucleus
as those in Ar.
C. Ar, because it is a heavier element.
D. Ar, because it has more electrons and they repel each other. - Answer- B
Out of Na+, Mg2+, Ne, and F- which has the smallest radius?
A. Na+
B. Mg2+
C. Ne
D. F- - Answer- B
When and where were the carbon and oxygen atoms in your body created?
A. In plants as they were growing
B. During the big bang
C. Within stars and stellar explosions
D. During the course of digesting your food - Answer- C
Iodine and silicone dioxide are both solid at room temperature. Which has a higher
melting point and why?
