Chemistry

6. What is the frequency of light (s-1) that has a wavelength of 1.23 x 10-6 cm

(a). 3.00 x 108 (b).2.44 x 1016 (c). 4.10 x 10-17 (d).9.62 x 1012 Explanation: The frequency and wavelength of electromagnetic radiation are related by the equation c = λν, where c is the speed of light (=3.00 x 108 m/s ), λ is the wavelength in m and ν is the frequency is s-1 or Hz. Since the wavelength is in cm it must be converted to meters before rearranging the above formula as follows: -6 1m -8 c 3.00"108 ms!1 16 1.23"10 cm"100cm =1.23"10 m,í = ë = 1.23"10-8 m = 2.44"10 s !1

11. What is the frequency (s-1) of a photon of energy 4.38 x 10-18J?

(a). 438 (b).1.45 x 10-16 (c). 6.61 x 1015 (d).2.30 x 107 Explanation: The frequency ν of this photon can be calculated by rearranging the equation E = h ν where E is the energy, h = Planck's constant and ν = frequency in s-1. E=híorí=E= 4.38"10!18J =6.61"1015s!1 h 6.626"10!34 Js

12. What is the wavelength (angstroms) of a photon of energy of 4.38 x 10-18J

(a). 438 (b).4.54x 10-8 (c). 454 (d).1.45 x 108 Explanation: The wavelength calculated here will be in meters which can be easily converted to angstroms as follows:

Ham radio operators often broadcast on the 6-meter band. The frequency of this electromagnetic radiation is __________MHz.

(a). 500 (b). 200 (c). 50 (d). 20 Explanation: The frequency and wavelength of electromagnetic radiation are related by the equation c = λν, where c is the speed of light (=3.00 x 108 m/s ), λ is the wavelength in m and ν is the frequency is s-1 or Hz. The frequency can be calculated by rearranging the above formula to get c 3.00!108ms"1 í = ë = 6 m = 50 MH

1. Electromagnetic radiation travels through vacuum at a speed of _________m/s.

(a). 6.626 x 1026 (b). 4186 (c). 3.00 x 108 (d).It depends on wavelength Explanation: The speed of light (electromagnetic radiation) through vacuum has a constant value of 3.00 x 108 m/s and is independent of the wavelength in vacuum.

10. The energy of a photon that has a wavelength of 13.2 nm is __________J.

(a). 9.55 x 10-25 (b).1.51 x 10-17 (c). 1.99 x 10-25 (d).4.42 x 10-23 Explanation: The wavelength is given in nm here which needs to be converted to meters and then the energy can be calculated as follows: 13.2nm" 1m =1.32"10!8m,E=(6.626"10!34Js)"(3.00"108m/s)=1.51"10!17J 109 nm 1.32"10!8 m

5. Of the following, __________ radiation has the shortest wavelength.

(a). X-ray (b). radio (c). microwave (d). ultraviolet Explanation: The wavelength and frequency are inversely related to each other, thus the radiation with the highest frequency (refer to figure 6.4 on page 219 from our text) will have the shortest wavelength.

What is the frequency (s-1) of electromagnetic radiation that has a wavelength of 0.53 m __________?

(a).5.7 x 108 (b).1.8 x 10-9 (c). 1.6 x 108 (d).1.3 x 10-33 Explanation: The frequency and wavelength of electromagnetic radiation are related by the equation c = λν, where c is the speed of light (=3.00 x 108 m/s ), λ is the wavelength in m and ν is the frequency is s-1 or Hz. The frequency can be calculated by rearranging the above formula to get c 3.00"108ms!1 8 !1 í = ë = 0.53m =5.7"10 s

21. The deBroglie wavelength of a particle is given by __________.

(a).h + mv (b). hmv (c). h/mv (d). mv/c

8. The wavelength of a photon of energy 5.25 x 10-19 J is __________m.

). 2.64 x 106 (b).3.79 x 10-7 (c). 2.38 x 1023 (d).4.21 x 10-24 !1 Explanation: The wavelength and energy are related by the formula E = hc/λ, where h is Planck's constant (= 6.626 x 10-34 Js), c is the speed of light (3.00 x 108 m/s) and λ is the wavelength in meters. The wavelength can then be calculated by rearranging the above formula as follows: E = hc or ë = hc = (6.626"10!34 Js)"(3.00"108 m/s) = 3.79"10!7 m ë E 5.25"10!19 J

What is the frequency of light (s-1) that has a wavelength of 3.12 x 10-3 cm __________?

a). 3.69 (b).2.44 x 1016 (c). 9.62 x 1012 (d).4.10 x 10-17 Explanation: The frequency and wavelength of electromagnetic radiation are related by the equation c = λν, where c is the speed of light (=3.00 x 108 m/s ), λ is the wavelength in m and ν is the frequency is s-1 or Hz. Since the wavelength is in cm it must be converted to meters before rearranging the above formula as follows: -3 1m -5 c 3.00"108 ms!1 12 3.12"10 cm"100cm=3.12"10 m,í=ë= 3.12"10-5 m =9.62"10 s

The energy of a photon of light is __________proportional to its frequency and __________proportional to its wavelength.

a). directly, directly (b).inversely, inversely (c). inversely, directly (d).directly, inversely Explanation: The energy is always directly proportional to the frequency while the frequency and wavelength of electromagnetic radiation are always inversely related to each other.

9. The energy of a photon that has a wavelength of 9.0 m is __________J.

a).2.2 x 10-26 (b).4.5 x 1025 (c). 6.0 x 10-23 (d).4.5 x 10-25 Explanation: The energy in Joules of any electromagnetic radiation whose wavelength is known can be calculated by the formula E = hc = (6.626"10!34 Js)"(3.00"108 m/s) = 2.2"10!26 J ë 9.0m