What is the wavelength of light when the electron in hydrogen atom undergoes a t

Question

What is the wavelength of light when the electron in hydrogen atom undergoes a transition from level n = 3 to level n = 2?(c = 3.00 times 10^8 m/s, h = 6.63 times 10^-34 J R_N = 2.179 times 10^-18 J) a. 3.89 times 10^-7 kJ/mol b. 1.7 times 10^-27 kJ/mol c. 2.57 times 10^6 kJ/mol d. 5.11 times 10^-19 kJ/mol e. 7.7 times 10^14 kJ/mol All of the following sets of quantum numbers are allowed EXCEPT a. n = 5, l = 3, m_t = 3 b. n = 4, l = 2, m_t = -2 c. n = 1, l = 0, m_t = 0 d. n = 1, l = 0, m_t = 0 d. n = 1, l = 0, m_t = 1 e. n = 6, l - 4, m_t = 4 What is the wavelength of a photon that has an energy of 3.097 times 10 J a. 3.1 times 10 nm b. 4.67 times 10 nm c. 6.42 times 10^-21 nm d. 9.29 times 10^21 nm e. 6.16 times 10 nm Which of the following sets of quantum numbers refers to a 4d orbital? a. n = 2, l = 1, m_t = -1 b. n = 2, l = 4, m_t = -1 c. n = 4, l = 2, m_t = -1 d. n = 4, l = 3, m_t = 0 e. n = 4, l = 3, m_t = +2 A possible value of the magnetic quantum number m_t for a 5p electron is a. 1. b. 4. c. -5. d. -6. e 3.

Explanation / Answer

25. [This question may be wrong. In the question they asked for the wavelength whereas the options provided are in kJ/mol(which is the unit of energy). If 'energy per electron' is calculated, option 'd' seems correct but the energy unit in the options do not match. 'kJ/mol' indicates energy calculated per mol. When energy is expressed in 'kJ/mol' unit, the calculated result does not match any one of the options.]

Energy per electron = R(1/n12   -   1/n22)

= (2.179 * 10-18 J)(1/4   -   1/64)

= 5.11 * 10-19 J

This is energy required per electron, for one mole energy required is:

= (5.11 * 10-19 J) * (6.023*1023 mol-1)

= 307775 J/mol

=307.775 kJ/mol

26. Answer: d

For principal quantum no = n, possible values of l = 0 to (n-1), possible values of ml = -l to +l

So when n = 1, possible values of l = 0, possible values of ml = 0. From n=1, ml can never be 1

27. Energy, E = hc/         ;where h = Planck's Constant, c = velocity of light, = wavelength

So, = hc/E = (6.626*10-34 J.s) * (3*108 m.s-1)/ (3.097 * 10 4 J)

= 6.42 * 10-30 m

= 6.42 * 10-21 nm (Ans: C)

28. For 4d orbital,

n= 4

l = 0,1,2,3 (Among these l=3 denotes 'd' orbital)

ml           = 0(for l=0)

               = -1,0,+1 (for l=1)

               = -2,-1,0,+1,+2 (for l=2)

               = -3,-2,-1,0,+1,+2,+3 (for l=3)

Ans: D

29. For 5p electron, value of l = 2 (as l=2 denotes 'p' orbital)

for l=2, ml = -2, -1 ,0 ,+1 ,+2

So answer is A.

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