BCHCT-131 EM 2025 SOLVED ASSIGNMENT

Description

ASSIGNMENT
Atomic Structure, Bonding, General Organic Chemistry
and Aliphatic Hydrocarbons
Core Course in Chemistry
Course Code: BCHCT-131
Assignment Code: BCHCT-131/TMA/2025
Maximum Marks: 100
Note: Attempt all questions. The marks for each question are indicated against it.
PART-(A)
1.
2.
3.
4.
5.
6.
7.
8.
How is the following expression for radius of hydrogen atom arrived at?
2
r

n

0


mZe
2
2
(a) Briefly explain Heisenberg uncertainty principle.
(b) Name the phenomena which can be explained using
(i) wave nature of radiation
(ii) particle nature of radiation.
Arrive at the time independent Schrodinger equation for a particle.
Explain the transformation of Schrodinger equation from Cartesian to spherical polar coordinates
and give its solution.
(a) Write the electronic configuration of the following:
Cl, Cr, Nb
(b) State aufbau principle.
First ionisation energies of second period elements show that the values increase from lithium to
beryllium, decrease for boron, and increase up to nitrogen, again decrease in oxygen and finally
increase up to neon. Explain.
Calculate the lattice energy (in Units kJ mol1) for ZnO crystal using electrostatic model
and using a Born-Haber cycle. Compare the two answers and comment on any difference.
Useful data:
Medelung constant (A) = 1.6411
Born Constant (n) = 8
Internuclear distance (a) = 199 pm
Zn(s) + ½ O2(g)  ZnO(s) Hf =  350.5 kJ mol1
Zn(s)  Zn(g)
HS = 130.4 kJ mol1
Zn(g)  Zn+(g) I(Zn) = 906.3 kJ mol1
Zn+(s)  Zn2+(g) I(Zn+) = 1733 kJ mol1
½ O2(g)  O(g) ½Hd = 248.5 kJ mol1
O(g)  O(g)
EA(O) = 141 kJ mol1
O-(g)  O2(g)
EA(O) = 780 kJ mol
a) i) Define formal charge. State the purpose of calculating formal charge of a molecule and write
its assumptions.
(50)
(5)
(2)
(3)
(5)
(5)
(3)
(2)
(5)
(5)
(2)
3
4

ii) Calculate the formal charges of NH3 and NH4
+.
b) Predict the molecular geometry of XeF4 and PCl5 molecules by using VSEPR theory. (3)
9. Draw the resonance structures of HCl. Out of them which one has little importance as a resonance
structure and why?
(5)
10. Write the molecular orbital configurations of 
2 O and
2 O. Calculate their bond orders and
comment on their magnetic nature.

PART-(B)
11. a) Write the chain isomers for a molecule having molecular formula C5H12. (2)
b) Write the geometrical isomers of 1,2-dimethylcyclopropane. Which one of them will have a
dipole moment and why?
(3)
12. Write the Fischer projections of stereoisomers of 2,3,4-trihydroxybutanal. Classify as them as
erythrose or threose type. Also mark their configuration as D or L.
(5)
13. Draw and explain various confirmations of butane. Which one of them is least stable and which one
is the most stable?
(5)
14. a) Write the resonance structures of ethanoate ion. Is the negative charge localised or not? (2)
b) Illustrate hyper conjugation with a suitable example. (3)
15. a) How does the stabilities of free radicals resemble those of carbocations? Explain with the help
of suitable examples.
(2)
b) Which out of the following pairs is more stable and why?
i) H3C – CH2 – CH – CH2CH3 or H3C – CH2 – O – CH2 – CH3
CH3
+ +

ii)
CH2
.
CH2
.
or

(3)
16. Briefly explain the following reactions and give their importance;
(i) Wurtz reaction
(ii) Sabatier-Senderen’s reaction
(5)
17. Explain the mechanism of Birch reduction giving a suitable example. (5)
18. Write the mechanism of hydration of 1-butene. (5)
19. Write the products formed when 2-pentyne undergoes ozonolysis. Give the mechanism involved. (5)
20. Draw the molecular orbitals of benzene and illustrate its electronic configuration.