#### Quantum Mechanical Model of Atom - Important Question Paper

11th Standard

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Chemistry

Time : 01:00:00 Hrs
Total Marks : 50

Part  A

10 x 1 = 10
1. According to the Bohr Theory, which of the following transitions in the hydrogen atom will give rise to the least energetic photon?

(a)

n = 6 to n = 1

(b)

n = S to n = 4

(c)

n = S to n = 3

(d)

n = 6 to n = S

2. Choose isosteres from the following

(a)

${ NO }^{ - }_{ 2 }and{ PO }^{ 3- }_{ 4 }$

(b)

${ NO }^{ - }_{ 2 }and{ O }_{ 3 }$

(c)

${ CO }_{ 2 },N_{ 2 }O,{ NO }^{ - }_{ 3 }$

(d)

${ CIO }^{ - }_{ 4 }\ and\ OCN^{ - }$

3. Which of the following is a pair of isoelectronic species?

(a)

${ CI_{ 2 }O }_{ 3 },ICl^{ - }_{ 2 }$

(b)

$ICl^{ - }_{ 2 },CIO_{ 2 }$

(c)

$IF^{ + }_{ 2 },I^{ - }_{ 2 }$

(d)

$CIO^{ - }_{ 2\ },CIF^{ + }_{ 2 }$

4. Which of the following statements about the electron is incorrect?

(a)

It is negatively charged particle

(b)

The mass of electron is equal to the mass of neutron

(c)

It is a basic constituent of all atoms

(d)

It is a constituent of cathode rays

5. According to Bohr's theory, the angular momentum of electron in 5th orbit is

(a)

$25\frac { h }{ \mu }$

(b)

$1.0\frac { h }{ \mu }$

(c)

$10\frac { h }{ \mu }$

(d)

$2.5\frac { h }{ \mu }$

6. The energy of second Bohr orbit of the hydrogen atom is $-328 KJ { mol }^{ -1 }$, hence the energy of fourth Bohr orbit would be

(a)

$-41\ KJ{ mol }^{ -1 }$

(b)

$-1312\ KJ{ \ mol }^{ -1 }$

(c)

$-164\ KJ{ \ mol }^{ -1 }$

(d)

$-82\ KJ{ \ mol }^{ -1 }$

7. Atomic emission spectra of an element cannot be used to

(a)

Identify the atom

(b)

determine the mass number of the nuclues of atom

(c)

measure the difference in energy between pairs of stationary state of atom

(d)

All of the above

8. RH (Rydberg constant) is x m-1 for H - atom. For He+ ion corresponding value for this constant is

(a)

100 x cm-1

(b)

400 x cm-1

(c)

4x cm-1

(d)

0.04 x cm-1

9. A continuum in spectrum is observed due to the following.

(a)

once an electron is completely free from the nucleus, it is no longer restricted to quantised discrete energy states.

(b)

electron takes up continuously the ordinary kinetic energy corresponding to its speed in free space

(c)

Both the reasons are correct

(d)

None of the reasons are correct

10. Given this set of quantum numbers for a multi - electron atom $2,0,0,\frac { 1 }{ 2 }$ and $2,0,0,-\frac { 1 }{ 2 }$. What is the next higher allowed set of n and l quantum numbers for this atom in its ground state ?

(a)

n = 2, l = 0

(b)

n = 2, l = 1

(c)

n = 3, l = 0

(d)

n = 3, l = 1

11. Part B

6 x 2 = 12
12. Define orbital? what are the n and 1 values for 3px and 4dx2-y2 electron?

13. The stabilisation of a half filled d - orbital is more pronounced than that of the p-orbital why?

14. How many orbitals are possible for n =4?

15. How many radial nodes for 2s, 4p, 5d and 4f orbitals exhibit? How many angular nodes

16. Write a note on Thomson's plum pudding model of an atom.

17. What did Rutherford's alpha ray scattering experiment prove

18. Part C

6 x 3 = 18
19. An electron a proton which one will have a higher velocity to produce matter waves of the same wavelength? Explain it

20. Explain why the uncertainty principle is significant only for the motion of sub-atomic particles but is negligible for the macroscopic objects?

21. How many orbitals are possible in the 4th energy level? (n = 4)

22. How many unpaired electrons are present in the ground state of Fe3+ (z=26), Mn2+(z=25) and argon(z=18)?

23. An ion with mass number 56 contains 3 units of positive charge and 30.4% more neutrons than electrons. Assign symbol to the ion.

24. The uncertainty in the position of a moving bullet of mass 10 g is 10-5 m. Calculate the uncertainty in its velocity?

25. Part D

2 x 5 = 10
26. By applying Bohr's postulates, arrive at the radius of nth orbit for hydrogen like atom

27. Write a note on limitations of Bohr's atom model.