GEN CHEM I EXAM III

Which of the following gases has the highest average kinetic energy at 298 K?

• O2

• CO2

• H2O

• H2

• all have the same kinetic energy

A sample of He gas effuses 5.73 times faster than an unknown gas. What is the molecular

mass of the unknown gas?

• 8.20 g/mol

• 2.02 g/mol

• 131 g/mol

• 70.9 g/mol

What are the two approximations that we make when assuming a gas is ideal?

An FM station broadcasts classical music at 93.5 MHz. Find the wavelength (in m) of these radio waves.

• 3.21x10^-7

• 3.21

• 2.81x10¹⁶

• 2.81

UVA and UVB are classifications of ultraviolet radiation. UVA waves have longer

wavelengths than UVB and are less dangerous. What is the energy of a photon of light of UVA

radiation having a wavelength of 320.0 nm?

A. 6.21×10 -28 J

B. 9.38×10 14 J

C. 7.07×10 -49 J

D. 2.07×10 -27 J

E. 6.21 x 10 -19J

(a)  

An atom emits a photon of light having a wavelength of 586 nm. Find the energy of this light

in units of kJ/mol.

A. 551 kJ/mol

B. 2.34×10 -7 kJ/mol

C. 661 kJ/mol

D. 3.36×10 -3 kJ/mol

E. 204 kJ/mol

(a)  

Which of the following sources produces the highest energy photons?

A. a doctor’s X-ray source

B. the heat lamp in a bathroom

C. a microwave oven

D. radio waves from a local station

E. gamma rays from a star

(a)  

The work function of sodium is φ = 2.9 × 10 -19 J. What is the maximum wavelength that can

cause ejection of photoelectrons from a sodium surface?

A. 151 nm

B. 222 nm

C. 45.1 nm

D. 451 nm

E. 685 nm

(a)  

De Broglie reasoned that for the electron in the hydrogen atom to behave as a stable circular

wave, the circumference of the electron’s orbit must be (a)  

A. equal to the wavelength of the electron wave.

B. an integer multiple of the electron’s wavelength.

C. a half integer multiple of the electron’s wavelength.

D. twice the wavelength of the electron wave.

E. twice the diameter of the orbit.

In the Bohr model of the atom, when an electron moves from a higher-energy orbit to a

lower-energy orbit, which of the following is observed?

A. the atom absorbs a photon of electromagnetic radiation.

B. the atom emits a photon of electromagnetic radiation.

C. the atom gains one unit of negative charge.

D. the atom emits an electron from a higher-energy orbit.

(a)