Chem 107 Exam III, Page 2 of 12 Nov 16, 2017 Multiple Choice 1. (3 points) In th

Question

Chem 107 Exam III, Page 2 of 12 Nov 16, 2017 Multiple Choice 1. (3 points) In the sunlight spectra, which color of light of the following has the highest frequency? A. red B. orange C. yellow D. green E. blue 2. (3 points) Calculate the frequeney of visible light having a wavelength of 486 nm A. 2.06 × 1014 B. 2.06× 10%-1 C. 0.17 × 1014 s-1 D. 1.20 × 10-15 s- E. 4.86 × 10-7 s-1 3. (3 points) What is the energy in joules of a mole of photons associated with visible light of wavelength 486 nm? A. 6.46× 10-16J B. 646 × 10-25J C. 2.46 x 10-4J D. 12.4kJ E. 246kJ 4. (3 points) Calculate the energy, in joules, required to excite a hydrogen atom by causing an electronic transition from the n1 to the n 4 principal energy level. A. 2.07×10-29J B. 2.19× 105J C. 2.04 × 10-18J D. 3.27 x 10-17J E. 2.25 x 10-18 J 5. (3 points) Calculate the wavelength of a neutron that has a velocity of 250 em/s. (The mass of a neutron 1.675 × 10-24g) A. 1.6 nm B. 0.016 nm C. 0.16nm

Explanation / Answer

Q1

highest frequency -.--> lowest wavlenght

in this case, it is violet/blue

from the list

choose E, blue

Q2

Freuqency = speed of light / wavleength

f = (3*10^8)/(486*10^-9) = 6.172*10^14 Hz or s^-1

choose C

Q3

E = hc/WL

E = (6.626*10^-34 )(3*10^8)/(486*10^-9) = 4.090*10^-19 J/photon

E = (4.090*10^-19)(6.022*10^23)/1000 = 246 kJ/

choose E

Q4

Apply Rydberg Formula

E = R*(1/nf^2 – 1/ni ^2)

R = -2.178*10^-18 J

Nf = final stage/level

Ni = initial stage/level

E = Energy per unit (i.e. J/photon)

E = (-2.178*10^-18)*(1/4^2 – 1/1 ^2)

E = 2.0418*10^-18

Q5

WL = h/(mV)

change mass to kg, and velocity to m/s

WL = (6.626*10^-34)/((1.675*10^-27)(2.5))

Wl = 1.582*10^-9 m

WL = 15.8 nm

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