IGNOU BCHCT-133 December 2020 Previous Year Question Paper

Q1.Write your Enrolment number, course code and part title clearly on each of the two answer books.

(iii) Marks are indicated against each question. Part—I (Max. Marks: 25) (Chemical Energetics and Equilibria) Note :Attempt any five questions from question nos. 1 to 7. Lot-Il 2.1. 0.

Q2.(a) What are intensive variables ? Identify intensive variables from the following: 2 @) Volume

(1) Refractive Index Gii) Temperature

(b) 1 mole of an ideal gas is made to expand from an initial volume of 2.24dm? to

Q3.2dm?® at 300 K. Calculate the maximum amount of work that can be produced in the surroundings by this process. 3 Derive a_ relationship between the temperature and volume for an adiabatic process.

Q4.(a) Calculate the amount of heat required to raise the temperature of 2 moles of water by 3°C. The specific heat capacity of water is given as 4.18 JK-1g71. 2 Give mathematical expression _for statistical definition of entropy and state the meaning of different terms involved in it.

(b) Derive the relationship between A, U and A,H for reactions involving gaseous reactants and/or products.

Q5.(a) What is Spontaneity ? Give criteria for spontaneity of a reaction in terms of

(i) entropy and

(ii) Gibbs energy. 2

(b) 2 moles of Argon gas is taken in a cylinder fitted with massless and frictionless piston and occupies a volume of 5 dm? at 298 K. The gas undergoes isothermal reversible expansion to 25dm?. If the gas behaves ideally, calculate the molar entropy change for the process. 3 Explain the difference between enthalpy driven and entropy driven reactions.

Q6.(a) “Chemical equilibrium is called a dynamic process.” Justify the statement. 2

(b) Write the expression for equilibrium constant, ky for the reaction : 2NO

(g) + O2

(g) 0 2NO9

(g) in terms of : G@) partial pressure and

(i) mole fraction of the gaseous species

Q7.(a) State the limitations of Arrheniu’s theory of acids and bases. 2

(b) One mole each of NO,

(g) and N,O,

(g) were mixed in a 1dm® flask and allowed to equilibrate. The following equilibrium was established : 3 If at equilibrium the reaction mixture contained 0.75 moles of N,O,

(g), calculate the value of equilibrium constant k, for the reaction. Explain the effect of addition of an inert gas on the following equilibrium reaction : 3 PCl;

(g) 0 PCl;

(g) + Clo

(e) (@) under conditions of constant pressure. Gi) under conditions of constant volume.

Q8.(a) What are buffer solutions ? Give an example of a basic buffer solution. 2

(b) Define degree of hydrolysis and derive a relationship between the degree of hydrolysis and hydrolysis constant for acetate ions.

Q9.(a) The sulphides of group IV cations are not precipitated in group II. Explain. 2

(b) How would the solubility of a sparingly soluble salt, Mg(OH), change on increasing the pH of the medium ? Explain. Calculate the pH of the following solutions : @ 100 cm? of 2x10? M HCl

(ii) 200 cm? of 1x 10-? M NaOH Part—II (Max. Marks: 25) (Functional Group Organic Chemistry—I) Note :Attempt any five questions from question nos. 8 to 14.

Q10.(a) What is Friedel-Craft’s alkylation reaction? Give an example. 2

(b) Write any three limitations of Friedel- Craft’s alkylation reactions.

Q11.Explain why —NO, group is metadirecting in electrophilic substitution reactions. Draw all resonance structures of carbocation formed by the attack of the electrophile on nitrobenzene to justify your answer.

Q12.(a) Taking a suitable example, write the mechanism of Sye reaction. 2

(b) How can the following conversions be carried out ? Answer any three : 3 @) Aniline to Chlorobenzene

(1) Iodobenzene to Biphenyl

(iii) Benzene to 1-bromo-4-nitrobenzene

(iv) Ethyne to Ethanol

Q13.(a) Why is thionyl chloride preferred for the conversion of alcohols to alkyl chlorides ? Write the mechanism of a reaction of thionyl] chloride with a primary alcohol. 3

(b) Write chemical equations for the following named reactions (any two) : 2 G) Reimer-Tiemann reaction Gi) Gattermann and Koch formylation

(ii) Rosenmund reaction

Q14.(a) How will you prepare methoxybenzene? 2

(b) Write the mechanism of the reaction of a Grignard reagent with acetone.

Q15.Write the mechanism of the following reactions (any two) : 5

(a) Claisen-Schmidt reaction

(b) Perkin reaction

(0) Benzoin condensation

Q16.Complete the following reactions (any five): 5 . _ (@) KCN/HCI Gi) Cf MeOH",

(ii) cr +R-C-Cl—A4_, CH,

(iv) CH3,CH, —-C — CH, non

(v) CH CH - CH - CH, —H!s_, OH OH Cr CH; wi) LO | +Cl, —Y+

(vii) CH,CH,CH, - Br + AgCN > uated aif

Q17.18 JK-1g"!)| 2 2170

(8) + 0,

(8) 0 270,

(8) PCI;

(g) 0 PCls

(g) + Cle) aif! . _ 6) KCN/HC1 Gi) Cf MeOHMH,0* OH II

(ii) cy +8-0-0--+ हक CH, OH OH cor

(vii) CH,CH,CH, - Br + AgCN > BCHCT-133 4,2

(40)