IGNOU BCHET-141 December 2025 Previous Year Question Paper

Q1.At 298 K, the resistance of 2.00 x 102 M KCl is 195.96 Q and that of 2.50 x 10-3 M KeSOu is 775.19 0. The conductivity (K) of 2x 102 M KCl at 298 K is 0.2768 Sm". Calculate molar conductivity of K2SOs solution.

Q2.What is thermogravimetric analysis ? Write the factors affecting TG curves.

Q3.Differentiate between atomic spectra and molecular spectra.

Q4.The molar absorptivity of a substance is 2 x 104 cm! mol! dm. Calculate the transmittance through a cuvette of path length 5 cm containing 2 x 10° mol dm? solution of the substance.

Q5.Briefly discuss the qualitative applications of IR spectrometry.

Q6.Give the merits and limitations of flame atomic emission spectrometry.

Q7.Write a short note on the sampling of soil.

Q8.Give a generalized molecular orbital energy level diagram for organic molecules and explain the possible transition among them.

Q9.The determination of iron in an iron-ore sample is carried out gravimetrically by five students. The percentages found are :

Q10.48, 67.47, 67.37, 67.40 and 67.43. Find the standard deviation, average deviation and probable deviation of a single determination and of the mean.

Q11.Explain the F-test and t-test.

Q12.Write short notes on the following : W428

(a) Extraction by Solvation

(b) Extraction by Chelation

Q13.Explain the potentiometric neutralization titration method.

Q14.What is the principle behind ion exchange chromatography ? How is it used to separate different ions in a mixture ?

Q15.How does adsorption chromatography separate components of a mixture and what factors influence the retention of compounds on the stationary phase ?

Q16.With the help of conductometric titration curves, discuss the titrations of weak acid with strong base and strong acid with weak base conductometrically.

Q17.19 Q $1 298 K ® 2 x 102 M KCl की

Q18.48, 67.47, 67-37, 67.40 और 67.

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