IGNOU BCHCT-135 December 2025 Previous Year Question Paper

Q1.(a) Explain whether the melting point of a substance will be lowered or raised by applying pressure if solid does not float on the liquid. 3

(b) Explain why molar conductance of a solution of electrolyte increases on dilution whereas the conductivity (specific conductance) decreases on dilution.

Q2.(a) From the data given below, predict whether the following redox reaction would be spontaneous or not : 2 8Ni(s) + 2Al°* (aq) —> 3Ni2* (aq) + 2Al(s) Given that : Ey yy = 70-25 V EA3+/a) = 71-66 V

(b) Briefly explain the following terms in the context of the phase diagram of condensed two-component systems: 3 @)_ Isopleth

(ii) Tie line Gii) Lever rule

Q3.(a) Explain why H* and OH™ ions in aqueous medium have exceptionally high ionic conductances. 3

(b) A conductivity cell with parallel electrodes was used to measure the resistance of solution. The resistance of a solution having specific conductivity equal to 1.5x 10°? Sem‘? is found to be 150 Q. If each electrode has an area

Q4.0 cm?, find the distance between them.

Q5.(a) Draw the temperature-composition diagram of a system exhibiting negative deviation from Raoult’s law and explain the distillation of such a mixture. 3

(b) Find the number of components for the following system : 2 NH,Cl(s) NHs3

(g) + HCl

(g) when : @ Pxu, = Puc Gi) Pn, * Pcl

Q6.The aqueous solution of an acid is provided with a platinum electrode around which hydrogen gas is bubbled at a pressure of 1 bar. The hydrogen electrode so obtained is combined with zinc electrode to construct a galvanic cell. If the e.m.f. of the cell at 298 K is found to be 0.39 V, find the pH of the solution. (Given that:E, 4, =-0.77V.) 5 Zn*" /Zn

Q7.(a) State Ostwald’s dilution law. 1

(b) At 18°C, the molar conductivities at infinite dilution of NaCl, NH4Cl and NaOH are 108.9, 129.8 and 217.4 S cm? mol!, respectively. If the molar conductivity of a 0.01 M solution of NH4OH is 9.33 S cm? mol-!, calculate its degree of dissociation of NH40OH at this dilution. 2

(c) What are the advantages of potentiometric titrations over conventional volumetric titrations?

Q8.(a) Derive Gibbs’ phase rule for a non- reactive system of C components having P phases. 3

(b) Differentiate between Galvanic and Electrolytic cells. 2 Part-B (Marks : 25)

Q9.Complete the following reactions : 5 6 CH, —C—c —H2PA=Be8 3 quinoline NHo ५६ NaNO, + HCl 9

(iii) O + CHCl, + 3Na0H —— ?

(iv) O + CgH;Cocl2O#_, ? CHO C _ By, 5

(v) (HOW) 4 moe! CH,OH

Q10.(a) Briefly explain cleansing action of soap. 2

(b) Write the steps involved in preparation of anilide (N-phenylbenzamide) from aniline.

Q11.(a) Arrange the following carboxylic acid derivatives in decreasing order of their reactivity towards nucleophilic acyl substitution, giving reasons : 3 oO oO @) CH; —C—O—C—CH, Gi) CH3;—C— NH, see ll Gii) CH, —C—Cl

(iv) CH3 —C —OCHg

(b) Which is more basic-methylamine or aniline ? Give reasons.

Q12.(a) “Direct nitration of aniline using nitric acid and sulphuric acid results in formation of large amount of meta- nitroaniline, in addition to the para- substituted products.” Explain. 2

(b) Why is sucrose known as an invert sugar ? 1

(c) How will you synthesize the following from diazonium salt ? 2 G@) 4-Bromo-1-methyl benzene Gi) Toluene

Q13.(a) What are epimers ? 1

(b) Name the linkage present in cellulose. 1

(c) Explain mutarotation taking example of glucose.

Q14.Write the steps involved in the preparation of alanine using Gabriel-Phthalimide synthesis.

Q15.(a) Differentiate among the primary, secondary and tertiary structure of proteins. 3

(b) Write Haworth structure of maltose. Name the monosaccharides present in it. 2 3Ni(s) + 2A1°* (aq) —> 3Ni?* (aq) + 2Al(s) रा i = —0.25 V Eas al =-1.66 V NH,Cl(s) NH3

(g) + HCl)

(ख) 18°C WR, aia Ta W NaCl, NH4Cl 2x

Q16.9, 129.8 3i% 217.4 S cm? mol" €1 afe 0.01 M NH.OH fara at Aree +) CH, —C—C] Hz/Pd-BaS0, NHo +s NaNO, + HCl 9

(1) ] tte? NHo

(iv) O + CgH,coc1 20H, ? CHO Cc —Br_, 9

(v) (CHOW), Fea wee? CH,OH

Q17.CH; —C—O—C—CH, Gi) CH3;—C— NH, Git) CH; —C—Cl

(iv) CH, —C — OCH, Gi) cea