1. What is the frequency (in Hz or sec - 1 ) ofelectromagnetic radiation that ha

Question

1.            What is the frequency (in Hz or sec-1) ofelectromagnetic radiation that has a wavelength of 1.23 x10-6 cm?

(A)            2.44 × 1016

(B)             2.44 × 1014

(C)             3.68 × 104

(D)            3.68 × 102

(E)             4.10 × 10-15

2.            Which of the following transitions in the Bohr hydrogen atomprovides the absorption of thehighest energy photon?

(A)            n=9 ® n=1

(B)             n=1 ® n=9

(C)             n=3 ® n=6

(D)            n=6 ® n=3

(E)             n=12 ® n=1

3.            An electron has a mass of 9.1 x 10-31 kg and an deBroglie wavelength of

           8.7 x 10-11 m. What is its velocity (in m/s)?

(A)            8.4 × 103

(B)             1.2 × 10-7

(C)             6.9 × 10-5

(D)            8.4 × 106

(E)             8.4 × 10-3

4.            What is H for the ionization of exactly one mole of hydrogenatoms?

(A)            +2.18 x 10-21 J

(B)             -2.18 x 10-21 J

(C)             +1.31 x 103 kJ

(D)            -1.31 x 103 kJ

(E)             None of the other answers are within 50% of the correct value

5.            Which of the following sets of quantum numbers (n,l, ml, ms)represents an acceptable set for an electron in a hydrogenatom?

(A)            2, 2, -1, -1/2

(B)             1, 0, 0, +1/2

(C)             3, 2, 3, +1/2

(D)            5, 4, -5, -1/2

(E)             5, 4, -3, +3/2

explain theanswers

Explanation / Answer

wavelength = 1.23 x 10-6 cm                     = 1.23 * 10 ^ -8 m So, frequency f = c / where c = speed of light = 3 * 10 ^ 8 m / s So,  f = 2.439 * 10 ^ 16 Hz (2).option ( B ) is correct (3).electron mass m = 9.1 x 10-31kg de Broglie wavelength = 8.7 x10-11 m we know = h / m v from this speed v = h / m where h = planck's constant = 6.625 * 10 ^ -34 J s            m= mass = 9.1 * 10 ^ -31 kg subsitue values we get v = 83.68 * 10 ^ 5 m /s       

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