IGNOU BCHCT-131 December 2020 Previous Year Question Paper

Q1.(a) With the help of a suitable diagram, briefly explain Sommerfeld modification to Bohr Atom Model. 4

(b) Write the electronic configuration of chromium. (Atomic No. of Cr = 24)

Q2.(a) What are the observed results of black body radiation experiment ? 3

(b) State Hund’s rule. What is the reason behind this rule ?

Q3.(a) What is a well behaved wave function ? Illustrate using suitable diagram/s. 3

(b) Write the resonance structures of hydrogen chloride. Which of these structures is the most important one ?

Q4.(a) Draw the shapes of three p-orbitals with appropriate labelling. 3

(b) Which one has higher lattice energy — KF or NaF ? Give reason why.

Q5.(a)

(i) Name the spectral lines of the atomic spectrum of hydrogen which appear in the visible region. 1 Gi) What are matter waves ? 1

(iii) Give the significance of y?. 1

(b) What is the hybridisation of each of the carbon atoms present in the compound HC =C-CH=CH ,?

Q6.(a) Compare any four properties of ionic and covalent compounds. 4

(b) Why is the dipole moment of BF3 zero ?

Q7.(a) Write the molecular orbital configurations of Og and 0; Also calculate their bond orders. 4

(b) How many chloride ions are present around a sodium ion in the sodium chloride crystal? 1 BCHCT-131 2 PARTB (Maximum marks : 25)

Q8.(a) Draw the enantiomers of 2-butanol. 2

(b) Which one will have lower pK, value — chloroethanoic acid or iodoethanoic acid ? Give reason for your answer.

Q9.(a) Write the geometrical isomers of HOOC — CH = CH - COOH. How can you differentiate between the isomers using a chemical reaction ? 3

(b) Why is aniline less basic than ammonia ? Explain.

Q10.(a) Write the mechanism of the reaction between ethyne and HBr. Also name the product formed. 3

(b) Which one of the following is more stable and why ? 2 H,CCH, or (CH,),CH

Q11.(a) Give the products formed by the Wurtz reaction involving bromoethane and 1-bromopropane. 3

(b) What is pericyclic addition ? Illustrate with the help of a suitable example.

Q12.(a) Write the mechanism of the reaction of propene with HBr in the presence of a peroxide. 3

(b) Write the structure of naphthalene and number of carbon atoms present in it.

Q13.(a) Draw various conformations of cyclohexane. 4

(b) State Hiickel’s rule.

Q14.(a) Write the mechanism of Wittig reaction. 4

(b) Write the IUPAC name of the following compound : 1 CH,CH,OH BCHCT-131 4 qe: BCHCT-131 6 H,CCH, 4 (CH,),CH CH,CH,OH