IGNOU BCHCT-131 December 2025 Previous Year Question Paper

Q1.Write your enrolment number, course code and part clearly on answer book.

(iii) Marks are indicated against each question. Part—A (Marks : 25) Note : Attempt any five questions.

Q2.(a) State the limitations of Bohr’s theory. 4

(b) What are matter waves ?

Q3.(a) Calculate the de-Broglie’s wavelength associated with a bullet having mass

Q4.2x10-3kg moving with a velocity of 30 ms-!. 2

(b)

(i) What is Laplacian operator ? 1 Gi) What is Hamiltonian operators? 1 Also give their significance.

Q5.(a) Explain why O3 is paramagnetic and o2* is diamagnetic. 3

(b) Write Lewis structures of NHj and co2- Oz.

Q6.(a) Define electron affinity. Write units used to measure it. 2

(b) Arrange the following in the increasing order of ionisation energy : 3 Be, B, N,O Also give reasons for your answer.

Q7.(a) State Aufbau’s principle with example. 2

(b) Write the electronic configuration of Copper (At. no. of Cu = 29). 1

(c) Write the hybridisation of each carbon atom in the following : 2 H,C — CH = CH — CHg

Q8.(a) Write the possible values of all the quantum numbers for all the electrons present in a 2p orbital. 4

(b) Using VSEPR theory, predict the shape of SF4.

Q9.(a) Write the resonance structures of NO3 ion. 3

(b) Draw the molecular orbitals formed by the combination of s-s atomic orbitals. Also name _ these orbitals. 2 Part—B (Marks : 25) Note : Attempt any five questions.

Q10.(a) Define Lewis acids. Which of the following are Lewis acids ? 2 CH; CHy, CH30CH3, CH3 C Ho, BF;

(b) @ Arrange the following groups in an ascending order of priority in assigning Z/E configuration : 2 — CH(CH3). — C(CH3)3, — CHy—CH,CH3

(ii) Draw the structure of isomer of CH3FC=CFCH3; which has a higher dipole moment.

Q11.(a) Explain with suitable structures as to why is allyl carbocation less stable than benzyl cation. 3

(b) What do you understand by Anti- Markownikoff’s addition ? Give one example of such a reaction.

Q12.(a) Complete the following : 3 CH,COO- —=2>5A——©%_, B dimerisation 6

(b) Write the products of the following reactions : 2 7 9 CHC ८ een BaSO, * HCH )C = CH —| NaNH, |, CH3CHeI

Q13.(a) Give one example each of the following with its structure : 3

(6) A bicyclic aromatic compound Gi) A heterocyclic aromatic compound Gii) An aromatic compound containing 147 electrons

(b) What is Sabatier-Sanderen’s reaction ? Give one example.

Q14.(a) What do you understand by the following ? 3 G@) Resolution Gi) Laevorotatory compound

(ii) Racemic mixture

(b) Write the reactions for the following: 2 Gi) Products of ozonolysis of butyne-2

(ii) Products of ozonolysis of butene

(2)

Q15.(a) Draw and name the most stable and the least stable conformations of butane. 2

(b) Define and give one example each of the following : 3 G@) An electrophile Gi) A nucleophile

(iii) A free radical

Q16.(a) Which of the following will be the strongest acid and why ? 2 CCl3,COOH, CH3;CH,COOH, CH,ClICOOH

(b) Complete the following reaction : 3 PhsP + CH3CH(X)CH3;—> A— Ceili. B (Ylide) c ec=o_ Bc=0 (Alkene) H,C - CH = CH- CHs CH, CH,, CH,OCH,, CH, CH,,BE, ~ CH,-CH,CH, CH,COO- —=24A—=©%2_, H, 7 eon : CH3CH,C =CH NaNHy CH;CH,I ~ ° CCl,COOH, CH,CH,COOH, CH,ClICOOH Ph3P + CH;CH(X)CH;—> A—Collsli_ छ