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Previous IIT-JEE Atomic Structure questions

Blazing goIITian

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14 May 2007 10:12:50 IST
Posts: 308
14 May 2007 10:12:50 IST
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Previous IIT-JEE Atomic Structure questions
Engineering Entrance , JEE Main , JEE Main & Advanced , Chemistry , Physical Chemistry , academic
1. How many photons of light having a wavelength of 420 nm are necessary to produce 1.2J energy ?
2. Calculate wave number and frequency of radiations having wavelength 5800.
3. Calculate the energy in eV of (i) He+ and (ii) Be 3- in the first excited state.
4. Calculate ratio of de-Broglie wavelength of electron to proton moving with a velocity of 10^5 m/sec.
5. Find out the number of waves made by Bohr electron in one complete revolution in its third orbit. Also calculate the number of revolutions per second that this electron makes around the nucleus?
6. Calculate uncertainty in position of a particle when uncertainty in the momentum is (a) 1 x 10^-2, gm cm sec^- 1 and (b) zero.
7. Calculate wavelength of radiation emitted producing a line in Lyman series when an electron falls from fourth orbit in Hydrogen atom.
8. The ionization energy of He+ is 19.6xl0^-18J per atom. Calculate the energy of second stationary state in Li2+ ion.
9. The uncertainty in first Bohr orbit is 1% of its actual value what will be the uncertainty in the velocity of electron? ( radius of first Bohr!s orbit = 0.53 A).
10. The electron energy in hydrogen atom is given by E(21.7x 10^12 /n^ 2 ergs). Calculate the energy required to remove an electron completely from n = 2 orbit. What is the longest wavelength in (cm) of light that can be used to cause this transition.?
11. With what velocity should an x-particle travel towards the nucleus of a copper atom so as to arrive at a distance 10^-13 metre from the nucleus of the copper atom.
12. An electron beam can undergo diffraction by crystals. Through what potential should a beam of electrons be accelerated so that its wavelength becomes equal to 1.54 A.
13. Calculate the de Broglie wavelength of the electron in the ground state of hydrogen atom, given that its kinetic energy is 13.6 eV. (leV = 1.602 x 10^-19J)
14. The circumference of the second Bohr orbit of electron in hydrogen atom is 600 nm. Calculate the potential difference to be applied between the plates so that the electrons have de Broglie wave length equal to this circumference.
15. Energy required to stop the ejection of electrons from Cu plate is 0.24 eV. Calculate the work function when radiations of k = 253.7 nm strikes the plate?

Ans.1. 2.535 x 10^18
Ans.2. 17240cm^-1, 5.172 x 10^14cps
Ans.3. -13.6eV , -54.4eV
Ans.4. 1887
Ans.5. 3, 2.42 x 10^14revolution
Ans.6. (1) 0.52 x 10^-27m (2) infinity
Ans.7. 97nm
Ans.8. -11.025 x 10^-18J
Ans.9. 1.094 x 10^8 m/s
Ans.10. 5.42 x 10^-12ergs, 3.67 x 10^-5cm
Ans.11. 6.3 x10^6 m/s
Ans.12. 63.57volt
Ans13. 0.3328 nm
Ans.14. 4.2 x 10^-6volt
Ans15. 4.65eV

Q1.Calculate the accelerating potential that must be imparted to a proton beam to give it effective wavelength of 0.005 nm
Q2.In a photoelectric effect experiment, irradiation of a metal with light of frequency 2.00 x 10^16 Hz yields electrons with maximum kinetic energy 7.5 x 10^-18 J. Calculat thershold frequency the metal.
Q3.Photoelectric emission requires a threshold frequency of vo. For a certain metal l 1=2200A and l2 = 1900A produce electrons with maximum kinetic energy KE1 and KE2. KE1 = KE2 calculate the corresponding wave length.
Q4.The dissociation I2 ----- 2I utilizes one photon per iodine molecule dissociated. The maximum wavelength for this is 4995 A. Calculate number of moles of I2 dissociated per kJ of photo energy.
Q5.Suppose 10^-17 J of light energy is needed by the interior of the human eye to see an object. How many photons of green light (wavelength-550 nm) are needed to generate this minimum amount of energy?
Q6.Consider the hydrogen atom to be a proton embedded in a cavity of radius a. (Bohr radius whose charge is neutralized by the addition of an electron to the cavity in vacuum, infin'tel slowly. Estimate the average total energy of an electron in its ground state in a hydroge atom as the work done in the above neutralization process. Also, if the magnitude of th average kinetic energy is half the magnitude of the average potential energy, find th average potential energy.
Q7.The reaction between H2 and-Br2 to form HBr in the presence of light is initiated by the photon decomposition of Br2 into free bromine atoms (free radicals) by absorption of light The bond dissociation energy of Br2 is 192 kJ/mole. What is the longest wavelength of the photon that would initiate the reaction?
Q8.A beam of electron accelerated with 4.64V is passed through a tube containing mercury vapours. As a result of absorption, electronic changes occured with mercury atoms and light was emitted. If the full energy of single electron was converted into light, what was th wave number of emitted light?
Q9.Light of wavelength 470 nm falls on the surface of potassium metal, electrons are emitted with a velocity 6.4 x 10^4 m/s.
(a) What is the kinetic energy of emitted electron?
(b) What is the minimum amount of energy required to remove an electron from atom?
Q10.O2 undergoes photochemical dissociation into one normal oxygen atom and one oxygen atom, 1.967 eV more energetic than normal. The dissociation Of 02 into two normal atoms of oxygen requires 498 kJ mole. What is the maximum wavelength effective for photochemical dissociation Of O2?
11. The ionisation energy of a H like Bohr atom is 4 Rydberg. (a) calculate the wavelength radiated when electron energy jumps from the first excited state to ground state. (b) What is the radius of I orbit of this atom?given I Rh = 2.18 x 10^- 18 J.
12. The minimum energy required to overcome the attractive forces between electron and the surface of Ag metal is 7.52 x 10^19- J. What will be the maximum kinetic energy of electron ejected out from Ag which is being exposed to UV light of l= 360 A'?
13. Find the quantum number 'n' corresponding to the excited state of He+ ion if on transition to the ground state that ion emits two photons in succession with wavelengths 108.5 and 30.4 nm.
14. To what series does the spectral lines of atomic hydrogen belong if its wave number is equal to the difference between the wave numbers of the following two lines of the Balmer series: 486.1 and 410.2 nm. What is the wavelength of that line?
15. The IP1 (ionisation Potential) of H is 13.6 eV. It is exposed to electromagnetic waves of 1028A and gives out induced radiations. Find the wavelength of these induced radiations.

Ans.1. 32.85 volt
Ans.2. 8.7 x 10^15 Hz
Ans.3. l0 = 2612.5A
v0 = 1.1483 x 10^15cps
Ans.4. 4.175 x 10 ^-3 moles of I 2
Ans.5. 28
Ans.6. T.E = -e^2/ 4p Î a
P.E = -e^2 /2 p Î a
Ans.7. 6235A
Ans.8. 37400/cn
Ans.9. (a) 1.86 x 10^-21J (b) 4.2 x 10^-19 J
Ans.10. 1047.5A
Ans.11. (a)303.89A (b) 2.645 x 10^-9cm
Ans.12. 47.68 x 10 ^-19J
Ans13. n = 5
Ans.14. Brackett Series, l = 2.63 x 10^-4cm
Ans15. I1 = 1029A, I2 = 1216A, I3 = 6568A.

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3 Aug 2012 21:27:04 IST
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ALL are easy questions guy

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