(Download) UPSC: Geologist Examination Papers-2020 (Chemistry Paper - 3)

(Download) UPSC: Geologist Main Examination Papers-2020

(Chemistry Paper-3)

Exam Name : UPSC Geo-Scientist and Geologist Main Exam

Subject : UPSC Geo-Scientist and Geologist Main Exam Papers 2020 : Chemistry Paper- 3

Year : 2020

Chemistry Paper - 3

Time Allowed : Three Hours
Maximum Marks : 200

SECTION A

Q1. (a) Round the following answers so that only significant figures are obtained : 1x5=5

(i) 2:4 + 0·010 + 6.24 = 8.65

(ii) 3.6 – 0.020 – 5:14 = - 1.56

(iii) (22 x 5.42) - 100.0 = 1.19

(iv) log 5.000 10^-4=-3-3010299

(v) Antilog 12.5 = 3.1622277 x 10¹²

(b) Particle diameter of stationary phase plays a critical role in chromatographic separations. Comment.

(c) Draw and state schematic diagram of non-dispersive IR photometer for monitoring CO in the air sample.
(d) Sketch the thermobalance used in TGA showing its key components.

(e) In X-ray fluorescence technique, matrix effects interfere in sample analysis. Comment and justify your answer.

(f) Describe three ways of introducing a sample into an ICP torch.

(g) How does CaCl, transform into excited Cao* during process occurring in flame ? Show schematically. How will you determine chromium ions spectrophotometrically in a mineral sample ?

Q2. (a) The solubility product (K_sp) of a salt is (41.2 + 0-3) × 10^-8. The molar solubility of salt in water is
Solubility = (K_sp)^1/2 = (41-2 x 10^-8)^1/2
= 6.418 x 10^-4 M
What is the uncertainty in the calculated solubility of salt in water ?

(b) Describe the equilibrium processes involved in solvent extraction of ions through chelation. Write the effect of pH and reagent concentration on the solvent extraction of a metal chelate.

(c) How will you determine the stoichiometry of metal : ligand in an iron (II) – 1,10-phenanthroline complex using slope-ratio and mole-ratio methods ?

(d) List the ways of calibrating TGA instrument.

Q3. (a) How will you analyse the mixture containing CaC₂O₄.H₂O, BaC₂O₄.H₂O and SrC₂O₄.H₂O by thermogravimetry ? State the strategy in brief.

(b) What are the advantages of temperature programming and pressure programming in Gas Chromatography (GC) ?

(d) How will you determine moisture content in a sample using Karl-Fisher reagent ? Describe the reactions involved in the method suggested. 3+7=10

Q4. (a) Define Specific Surface Area (SSA).
A solid cube weighing 2:0 g was divided into 1000 smaller cubes. If the solid cube is having volume 1 cm", calculate SSA of the smaller cube. A sample of feldspar weighing 0-5140 g was found to contain 0.0812 g of total of chlorides of sodium and potassium. On further treatment, it gave 0.1450 g of potassium hexachloroplatinate precipitates [FW = 485.95). Find out % of Na₂O in the feldspar sample.

[K₂O = 94, Na₂O = 62, NaCl = 58-5, KC1 = 75.5]

(ii) Discuss the advantages and disadvantages of alumina (A1,0z) as stationary phase in TLC.

(d) A 5.00 mL sample was treated with reagent to generate a colour with phosphate. Subsequently the sample was diluted to 100 mL. To a second 5.00 mL sample was added exactly 10.00 mL of a phosphate solution containing 0.05 mg phosphate/mL, which was treated in the same way as the original sample. The absorbance of the first solution was 0.525 and that of the second was 0.635. Calculate the concentration of
phosphate in mg/mL of the sample.

Q5. (a) A mixture containing 8-hydroxyquinoline-complexes (AIQ₃ and MgQ₂) of aluminium and magnesium weighed 1.0981 g. They left the mixture of Al₂O₃ and MgO as a residue weighing 0.1354 g, when ignited in the air. [Al₂O₃ = 101.96, MgO = 40-30, AlQ₃ = 459-44, MgQ₂ = 312-61] Describe spectrophotometric analysis of

(i) A sample containing one absorbing component.
(ii) A sample containing two absorbing components. HJI-T-CHEM

(c) Derive a balanced chemical reaction for the redox reaction in acidic medium.
(d) Determination of vitamin in a food sample was carried out by a routine voltammetric method and by Flow Injection Analysis (FIA). Following results were obtained :