Emission and Absorption Spectra

Q. The wavlength of a spectral line for an electronic transition is inversely related to:

1. The number of electrons undergoing the transition
2. Mass of the atom
3. The difference in the energy of the energy levels involved in the transition
4. The velocity of electrons undergoing the transition

Q. Which of the following ligands causes maximum crystal field splitting?

1. $SC{N}^{-}$
2. $en$
3. $C_2{O}_4{}^{2-}$
4. $N{H}_3$

Q. For a hydrogen atom, ultraviolet radiation corresponds to which transition series?

1. Lyman series
2. Balmer series
3. Paschen series
4. Brackett series

Q. Find the wavelength of the limiting line in the Lyman series of the hydrogen spectrum? $(R=1.097\times {10}^{-2}{\text{nm}}^{-1})$

1. $94.21\text{nm}$
2. $91.16\text{nm}$
3. $911.6\text{nm}$
4. $933.6\text{nm}$

Q.

In a Bohr's model of atom when an electron jumps from n=1 to n=3, how much energy will be emitted or absorbed

1. $2.15\times {10}^{-11}erg$

2. $0.1911\times {10}^{-10}$ erg

3. $2.389\times {10}^{-12}$ erg

4. $0.239\times {10}^{-10}$ erg

Q. If the first excitation energy for an H-like (hypothetical) sample is 24 eV, then the separation energy of an electron in the 3rd excited state is:

1. 2 eV
2. 3 eV
3. 4 eV
4. 5 eV

Q. In a collection of H-atoms, all the electrons jump from $n=5$ to the ground level (directly or indirectly) without emitting any line in the Balmer series. The number of different possible radiations is:

1. $10$
2. $8$
3. $7$
4. $6$

Q. The spectrum produced by white light is:

1. An emission spectrum
2. A continuous spectrum
3. An absorption spectrum
4. Both emission and continuous spectrum

Q. According to Bohr's model of atom an electron revolves around the nucleus in following fashion

1. Circular orbit
2. Elliptical orbit
3. Spiral orbit
4. None of the above

Q.

The energy of a K-electron in tungsten is $-20keV$ and of an L-electrons is $-2keV$. The wave length of X-rays emitted when there is electron jump from L to K shell :-

1. $0.3443Ă$

2. $0.6887Ă$

3. $1.3982Ă$

4. $2.78Ă$

Q. How many spectral lines will be observed when an electron jumps from the $5^{th}$ excited state to the ground state in the visible line spectra of H-spectrum?

1. 4
2. 5
3. 3
4. 6

Q. Number of visible lines when an electron returns from $5^{th}$ orbit to $2^{nd}$ orbit in H-spectrum:

1. 5
2. 4
3. 3
4. 10

Q. For which of the species is Bohr's theory not applicable?

1. $B{e}^{3+}$
2. $L{i}^{2+}$
3. $H{e}^{2+}$
4. $H$

Q. The wavelength of the radiation emitted when a hydrogen atom electron falls from infinity to 2nd excited state would be: (Rydberg constant $=1.097\times {10}^7{m}^{-1})$

1. 406 nm
2. 192 nm
3. 821 nm
4. 168 nm

Q. The Line spectra of two elements are not identical because:

1. The elements do not have the same number of neutrons
2. They have different atomic numbers
3. Their outermost electrons are at different energy levels
4. They have different valencies

Q. Calculate the energy of radiation emitted for the electronic transition from infinity to ground state for $L{i}^{2+}$ ion.
$(\text{Given}:c=3\times {10}^8\text{m/s},R_H=1.09678\times {10}^7{\text{m}}^{-1}$
$h=6.626\times {10}^{-34}{\text{J s}}^{-1})$

1. $19.66\times {10}^{-18}\text{J}$
2. $17.66\times {10}^{-18}\text{J}$
3. $9.83\times {10}^{-18}\text{J}$
4. $8.83\times {10}^{-18}\text{J}$

Q. What is the maximum wavelength line in the Lyman series for $H{e}^{+}$ ion?

1. $3R$
2. $\frac{1}{3R}$
3. $\frac{4}{4R}$
4. None of these

Q. When an electron makes a transtion from its $n+1$ state to the $nth$ state, the frequency of the emitted radiations is related to $n$ according to (where $n>>1)$:

1. $v=\frac{2cR{Z}^2}{n^3}$
2. $v=\frac{cR{Z}^2}{n^4}$
3. $v=\frac{cR{Z}^2}{n^2}$
4. $v=\frac{2cR{Z}^2}{n^2}$

Q. A laser light radiation is being studied in a spectrometer. The spectrum produced by the LASER will be:

1. Line spectrum of a single colour is obtained
2. A band spectrum with many different sets of wavelengths depending on the power of source
3. Continuous spectrum of white light
4. Different colored patches are observed

Q. Calculate the wavelength of radiation emitted when an electron falls from third excited state to ground state in the Lyman series of Hydrogen atom.
($R_H=1.1\times {10}^7{m}^{-1})$

1. $\lambda =1.83\times {10}^{-7}m$
2. $\lambda =0.97\times {10}^{-7}m$
3. $\lambda =0.97\times {10}^{7}m$
4. $\lambda =1.83\times {10}^{-8}m$

Q.

When an electron jumps from L to K shell

1. Energy is absorbed

2. Energy is released

3. Energy is sometimes absorbed and sometimes released

4. Energy is neither absorbed nor released

Q. Calculate the wave number for the shortest wavelength transition in Brackett series for atomic hydrogen.

1. $6.5\times {10}^6{\text{m}}^{-1}$
2. $6.75\times {10}^4{\text{m}}^{-1}$
3. $6.85\times {10}^5{\text{m}}^{-1}$
4. $6.9\times {10}^7{\text{m}}^{-1}$

Q. How do the energy gaps between successive electron energy levels in an atom vary from low to high $n$ values?

1. All energy gaps are the same
2. All energy gaps decreases as $n$ increases
3. All energy gaps increases as $n$ increases
4. The energy gap changes unpredictably as $n$ increases

Q. Which of the following transition corresponds to the second line in Balmer series?

1. 2 $\to$ 1
2. 3 $\to$ 2
3. 4 $\to$ 2
4. 3 $\to$ 1

Q. Of the following transition in $H$-atom, the one which gives an absorption line of maximum wavelength is:

1. $n=1\to n=2$
2. $n=3\to n=8$
3. $n=2\to n=1$
4. $n=3\to n=1$

Q. What is the maximum wavelength line in the Lyman series for $H{e}^{+}$ ion?

1. $3R$
2. $\frac{1}{3R}$
3. $\frac{4}{4R}$
4. None of these

Q. The energy of an electron in the second and the third Bohr's orbits of a hydrogen atom is $-5.42\times {10}^{-12}\text{erg}$ and $-2.41\times {10}^{-12}\text{erg}$ respectively. Calculate the wavelength of the emitted radiation when the electron drops from the third to the second orbit.

1. $5603\stackrel{o}{\text{A}}$
2. $6603\stackrel{o}{\text{A}}$
3. $7603\stackrel{o}{\text{A}}$
4. $8603\stackrel{o}{\text{A}}$

Q. Which electronic transition in a hydrogen atom, starting from the orbit $n=7$, will produce infrared light of wavelength 2170 nm?
(Given: $R_H=1.09677\times {10}^7{m}^{-1}$)

1. $n=7\to n=6$
2. $n=7\to n=5$
3. $n=7\to n=4$
4. $n=7\to n=3$

Q. If ${\lambda }_{L1},{\lambda }_{L2}$ and ${\lambda }_{L3}$ are wavelengths of $1^{st},2^{nd}$ and $3^{rd}$ lines of Lyman series ${\lambda }_{B1},{\lambda }_{B2}$ and ${\lambda }_{B3}$ are wavelengths of $1^{st},2^{nd}$ and $3^{rd}$ lines of Balmer series while ${\lambda }_{P1}$ and ${\lambda }_{P2}$ are wavelengths of $1^{st},2^{nd}$ lines of Paschen series of hydrogen then which of the following relations is/are correct?

1. $\frac{1}{{\lambda }_{L3}}=\frac{1}{{\lambda }_{P1}}+\frac{1}{{\lambda }_{B1}}+\frac{1}{{\lambda }_{L1}}$
2. $\frac{1}{{\lambda }_{B3}}=\frac{1}{{\lambda }_{P2}}+\frac{1}{{\lambda }_{B1}}$
3. $\frac{1}{{\lambda }_{B3}}=\frac{1}{{\lambda }_{B2}}+\frac{1}{{\lambda }_{B1}}$
4. $\frac{1}{{\lambda }_{B2}}=\frac{1}{{\lambda }_{B1}}+\frac{1}{{\lambda }_{P1}}$

Q. Calculate the wavelength of radiation emitted when an electron falls from third excited state to ground state in the Lyman series of Hydrogen atom.
($R_H=1.1\times {10}^7{m}^{-1})$

1. $\lambda =1.83\times {10}^{-7}m$
2. $\lambda =0.97\times {10}^{-7}m$
3. $\lambda =0.97\times {10}^{7}m$
4. $\lambda =1.83\times {10}^{-8}m$