IGNOU BCHCT-133 December 2022 Previous Year Question Paper

Q1.(a) What are extensive variables ? Identify extensive variable(s) from the list given below : Refractive index, temperature, volume 2 Calculate the amount of heat required to increase the temperature of 2-0 moles of Helium gas from a temperature of 300 K to 500 K under isochoric conditions. 2 [Given: Cy. m = 12-48 JK-1 mol}

(b) Define and differentiate between state functions and path functions giving suitable examples.

Q2.(a) What do you understand by entropy of a system ? Give its units and write the general expression for the entropy change for a _ process involving _ reversible isothermal expansion of an ideal gas. 2 Elemental sulphur undergoes a _ phase transition from orthorhombic form to monoclinic form at 363 K. If the molar enthalpy of the transition is — 402 J mol}, calculate the entropy of transition. 2

(b) State Hess’s Law of Constant Heat Summation and calculate the value of AH° for the following reaction at 298 K. 3 C (graphite) + 5 0g

(g) > CO

(g) BCHCT-133 2 You may use the following thermochemical equations : C (graphite) + O,

(g) > CO,

(g) AH? = — 393-5 kJ mol! CO

(g) + 5 Og

(g) > COg

(g) AH? = — 283-5 kJ mol

Q3.(a) Define spontaneity. Can the decrease in enthalpy act as a criterion for spontaneity ? Justify your answer. 2

(b) The standard enthalpies of formation of C,H;0H (J), CO g

(g) and H,OW) are —277-:0, -393-5 and —285-5kJ mol! respectively. Calculate the standard enthalpy change for the following reaction : 3 C,H;0H (J) + 3 Og

(g) > 2 COzg

(g) + 3 HAO (/)

Q4.(a) Chemical equilibrium is a dynamic process. Explain. 2

(b) State Le-Chatelier’s principle and explain the effects of

(i) decrease in pressure, and

(ii) increase in temperature on the following reaction : 3 2 SOQ

(g) + Og

(g) = 2 SOs

(g), A\H® = — 194 kJ mol}.

Q5.(a) State any two limitations of Arrhenius theory of acids and bases. 2

(b) How are K, and K, related for a reaction involving gaseous reactants and/or products ? If the value of K, for the following reaction at 303 K is 7:14 x 10-° Pa, calculate the value of K, at this temperature. 3 Calculate the degree of ionisation of formic acid in its 0-01 M aqueous solution. 3 (Given : K, (HCOOH) = 1 x 1074)

Q6.(a) Calculate the hydroxide ion concentration of an aqueous solution having a pH = 4-0. 2 What are buffer solutions ? Give an example of buffer solution. 2

(b) Arrange propanoic acid, ethanoic acid and 2-chloroethanoic acid in the increasing order of their acidities giving reasons.

Q7.(a) What is meant by ‘salting out’ of soap ? 2 If the value of Ky for sparingly soluble salt, PbCl, is 1:6 x 10-5, calculate its solubility in water. 2

(b) Define salt hydrolysis and calculate the degree of hydrolysis of ammonium ions in 0:001 M aqueous solution of ammonium chloride at 298 K. 3 (Given : K, (NH,OH) = 1:8 x 10-5 at 298 K) PART B (Maximum Marks : 25) Functional Group Organic Chemistry-I Attempt any five questions from questions no. 8 to 14.

Q8.(a) 1,3,5-cycloheptatrienyl cation is aromatic whereas 1,3,5-cycloheptatriene is not. Explain. 2

(b) Complete any three of the following reactions : 3 . Pt eS “610K NHNH, Oe te® _, ii + 2 2"? (HOCH, CH,),0 0 0 © I I Gi) Co + CoH; -C-0-C-CjH; —> CO 21014 Gv) CO + CH,CH,Cl ——2>

Q9.Halogen groups are electron withdrawing yet ortho, para directing in electrophilic substitution reactions. Explain.

Q10.(a) Explain the mechanism of Sy1 reaction with the help of a suitable example. 3

(b) Complete the following reactions : 2 SOCl,

(i) | CH3;CH,CH,0H ———> \ CH;CH,OH

Q11.(a) The dipole moment of chlorobenzene is lower than that of chloro-cyclohexane. Explain. 2

(b) How can the following conversions be carried out ? Answer any three. 3 G@) —_1-Propene to 1,2-Dibromopropane

(ii) Aniline to Chlorobenzene Gii) 1-Chloro-4-Nitrobenzene to 4-Nitroaniline

(iv) Benzene to 1-Bromo-4-Nitrobenzene

Q12.Give the mechanism of any two of the following : 5

(6). p-Chlorotoluene > 4-Methylaniline + 3-Methylaniline

(ii) 1-Chloro-4-Nitrobenzene > p-Nitrophenol

(iii) 2-Bromopropane > Propene

Q13.Give chemical equations for any five of the following named reactions : 5

(i) Rosenmund reduction

(ii) Houben-Hoesch reaction

(iii) Reimer-Tiemann reaction

(iv) Benzoin condensation

(v) Friedel-Crafts acylation

(vi) Gattermann-Koch formylation

(vii) Perkin reaction

Q14.Complete any five of the following reactions : 5 Cy dr;

Q15.CT + 2Na + CH,CH,Br = CO cuy,cuc “Cs Gi) O + (CH3),CHCL ——2> CY Clay, light tae N,Cl है Cr 2 6) HBF,

(ii) A | Cu

(v) H3;C-C-OH — I 573 K CHg CH(CH. wi) [LT 4,

(ii) H,SO,

(vii) R-C-R+R’COOOH —> BCHCT-133 8 qe: BCHCT-133 10 AH? = — 393-5 kJ mol! AH? = — 283-5 kJ mol! C,H;OH (J) + 3 O,

(g) > 2 CO,

(g) + 3 छ,0 0) 280५

(8) + 0,

(8) ल्‍ 2 50६

(8), A,H° = —194kJ mol (feat wat @ : K, (HCOOH) = 1 x 10-4) BCHCT-133 12 - Pt

(i) CH, (CH);CHg me COCH, KOH, H,O Oo + NIDNH OCH, CH,),0 0 0 oO ll ll

(iii) Co + CoH; -C-O-C-C,H,; —>

(iv) CO + CH,CH,Cl ACs SOCl,

(i) CH,CH,CH,0OH ———> CH; CH.C \ H,CH,OH CH, BCHCT-133 14

(i) Cy + 2Na+CH3CH,Br —— AICI, Gin Oo + (CHy)CHC] ——> toe NjCl है Cy 2 6) HBF,

(ii) A CH, | Cu

(v) H;C-C-OH —+s | 573 K CH, CH(CH w) Ue 2g

(ii) H,SO,

(vii) R-C-R+R'COOOH —>