QP-CGeoScnstM-26-220626-CHEMISTRY-PAPER-III

Combined Geo-Scientist (Main) Examination, 2026 SNCS-C-CMS CHEMISTRY PAPER—III Time Allowed : Three Hours Maximum Marks : 200 QUESTION PAPER SPECIFIC INSTRUCTIONS Please read each of the following instructions carefully before attempting questions There are TEN questions divided under TWO Sections. Candidate has to attempt SIX questions in all. Question No. 1 in Section—A and Question No. 6 in Section—B are compulsory. Of the remaining questions, candidates have to answer FOUR questions, choosing TWO from each Section. The number of marks carried by a question/part is indicated against it. Neat sketches are to be drawn to illustrate answers, wherever required. These shall be drawn in the space provided for answering the question itself. Unless otherwise mentioned, symbols and notations have their usual standard meanings. Assume suitable data, if necessary, and indicate the same clearly. Attempts of questions shall be counted in sequential order. Unless struck off, attempt of a question shall be counted even if attempted partly. Any page or portion of the page left blank in the Question-cum-Answer (QCA) Booklet must be clearly struck off. Answers must be written in ENGLISH only. SNCS-C-CMS/73 1 [ P.T.O. 1. (a) (b) () (4) (e) (9) SECTION—A A geologist received certain samples as follows : Sample Weight of sample (g) Sample 1 2:50x107} Sample 2 2:40x1073 Sample 3 5-00x107> Sample 4 150x107 Sample 5 7-00x1075 Sample 6 175x107 Sample 7 0:75x107} Classify the above samples as per their respective sample size following the sampling protocol for analytical chemist. In gas chromatography, what is the effect of stationary-phase film thickness on gas chromatograms? An amine sample is analyzed as the picrate derivative. A 0:05 g sample is reacted with picric acid and diluted to 1L deionized water. The solution exhibits an absorbance of 0:40 in a 1 cm cell. What is the percentage of amine in the sample? [Amax =359nm; €= 1:25x104 cm™! mol! L; formula weight of the amine = 310] What is the principle used in VG-AAS? Give the names of two elements that are measured with better detection limit using VG-AAS than by flame AAS. Name three gases used for purging in thermogravimetric analysis (TGA). Justify your answer. What is the cause of fluorescence in X-ray diffraction? How does fluorescence phenomenon impact X-ray diffraction data? (i) What is the purpose of using argon gas in ICPMS? (ti) Why is HCl or HC1O, not recommended for sample preparation for arsenic analysis by ICPMS? SNCS-C-CMS/73 2 (h) A solution comprising 1:0 g pyrolusite is treated with 100 mL of 0:1 N oxalic acid and H2,SO,4. The excess oxalic acid requires 27 mL of 0:05 N KMnO, for complete titration. Find the amount of MnO, (in wt%) in the sample. [Given : Molar mass of MnO, = 87 g mol”?] 5 2. (a) The first three peaks in an X-ray diffractogram (XRD) of metal M are obtained at 20 values of 38°6°, 557° and 70-0°, using Cu Ka radiation (A = 1:542 A). Compare the crystal structure and atomic radii with those given in the table below, and identify M : Metal Crystal structure Atomic radius (A) Al FCC 1:431 Au FCC 1-442 Pt FCC 1:387 Cr BCC 1:249 Mo BCC 1:363 Ta BCC 1-429 Ti HCP 1-445 Zn HCP 1-332 Cd HCP 1-490 15 (b) (i) Why is quantitative analysis of Fe** by spectrophotometric method drastically improved by complexation with 1,10-phenanthroline? What analytical parameters are improved? 3+4 (ii) How will you validate the above method of analysis? 3 (c) How can the age of a geological deposit be determined by ICPMS analysis? 5 3. (a) Aluminium (Al) content (in g) in a 100 g bauxite sample is determined by two different laboratory methods, as given below : Sl. No. Method-A Method-B 1s 51:0 51-1 2. 51:9 52:0 3. 52°3 52:7 4. 54-4 54-6 5. 50:9 51:2 6. 53:1 53-4 Calculate the ‘variance’ of the analyses by both methods (A and B) above and compare their precision through F-test, and state which of the methods, A or B, is significant for analysis of Al in bauxite ore. [F-table is provided in the next page] 10 SNCS-C-CMS/73 3 [P:T.O. F-table Probability 2 $, (corresponding to greater mean square) devel 1 2 3 4 5 6 7 8 9 10. 15 0:10 1 39:9 495 536 558 572 S582 589 594 599 602 61:2 63:3 0-05 161-4 1995 215:7 2246 230:2 2340 2368 2389 2405 241:9 2460 2543 0-01 4052 4999 5403 5625 5764 5859 5928 5981 6023 6056 6157 6366 0:10 2 8:53 9:00 916 9:24 929 933 935 937 938 939 942 949 0-05 18:5 19:0 19-2 19-2 19:3 19:3 19-4 19-4 19-4 19-4 19-4 19:5 0-01 985 990 992 992 993 993 994 994 994 994 994 995 0:10 3 5:54 546 539 534 531 5:28 527 $25 524 523 520 S13 0-05 10-1 9-55 9:28 9:12 9:01 8-94 8:89 8-85 8-81 8-79 8-70 8:53 0-01 341 30:8 295 287 282 279 27-7 275 273 272 269 261 0:10 4 454 4:32 419 411 405 401 3-98 3-95 3:94 3-92 3:87 3-76 0-05 771 694 659 639 626 616 609 604 600 596 586 562 0-01 21:2 18:0 16-7 16:0 15:5 15-2 15:0 14:8 14-7 145 14-2 13-5 0-10 5 4-06 378 362 352 345 340 337 334 332 330 324 310 0-05 661 579 541 519 505 495 488 482 477 474 462 436 0-01 16:3 13:3 121 11-4 11-0 10:7 10-5 10:3 10-2 10-1 972 9:02 0-10 6 3-78 346 3:29 318 311 305 301 298 296 294 287 2-72 0-05 5:99 514 476 453 439 428 421 415 410 406 394 367 0-01 13-7 10:9 978 915 875 847 826 810 798 787 756 688 0:10 7 3:59 326 307 296 288 2:83 278 275 272 270 263 247 0-05 5:59 474 435 412 397 387 379 373 368 364 351 3:23 0-01 12:2 9:55 845 7:85 7-46 7:19 6:99 6:84 672 6°62 631 5-65 0-10 8 3-46 3:11 2:92 281 2:73 267 262 259 256 254 246 2:29 0-05 5:32 446 407 3:84 3:69 3:58 3:50 3:44 3:39 3-35 3:22 2:93 0-01 11:3 865 759 7:01 663 637 618 603 S91 581 5:52 486 0-10 9 3:36 3:01 2:81 269 261 255 2:51 247 244 242 2:34 2:16 0-05 5:12 426 386 363 348 337 329 323 318 314 301 271 0-01 10-6 802 699 642 606 580 S61 547 535 526 496 431 0-10 10 3-29 2:92 273 2-61 252 246 241 238 235 2:32 2:24 2:06 0-05 4-96 410 3-71 3:48 3:33 3-22 3-14 3:07 3:02 2:98 2:85 2:54 0-01 10:0 756 655 5:99 5-64 5:39 5:20 5:06 4:94 485 456 3-91 0-10 12 3-18 2:81 261 2:48 2:39 2:33 2:28 2:24 2:21 2:19, 2:10 1:90 0-05 4-75 389 349 326 311 300 291 285 280 275 262 2:30 0-01 9:33 693 S95 541 506 482 464 450 439 430 401 3:36 0-10 15 3:07 270 249 2:36 227 2:21 216 212 209 2:06 1:97 1-76 0-05 4:54 368 329 306 290 279 271 264 259 254 240 207 0-01 8-68 6:36 542 489 456 432 414 400 389 380 352 287 0-10 16 3-05 2:67 2:46 2:33 2:24 2:18 2:13 2:09 2:06 2:03 1:94 1:72 0-05 4-49 3-63 3-24 3:01 2-85 2-74 2-66 2:59 2:54 2:49 2:35 2:01 0-01 8-53 6:23 5:29 477 444 4:20 403 3-89 3-78 3-69 3-41 2-75 0-10 24 2:93 254 233 219 210 2:04 1:98 1:94 1:91 1:88 1:78 1:53 0-05 4:26 340 301 278 262 251 242 236 230 225 211 1:73 0-01 7-82 561 472 422 390 367 350 336 326 317 289 221 0-10 60 2:79 239 218 2-04 1:95 1:87 1-82 LT 1:74 1-71 1-60 1:29 0-05 4:00 315 276 253 2:37 225 217 210 2:04 1:99 1:84 1:39 0-01 7-08 498 413 365 334 312 295 282 272 263 235 1-60 0-10 © 271 2:30 2:08 1:94 1:85 1:77 1:72 1-67 1-63 1-60 1:49 1-00 0-05 3-84 300 260 237 2:21 210 201 1:94 1:88 1:83 1-67 1:00 0-01 6-63 461 378 332 302 280 264 251 2-41 2:32 2:04 1:00 SNCS-C-CMS/73 4 (b) (c) (4) () The following data is given for Fe analysis by atomic absorption spectrometry : Concentration of Fe (mg/L) Instrument response (absorbance) 0-000 0-040 2-000 0-150 5-000 0-380 15-000 1-020 Unknown 0-832 The least square fit of the calibration data is given as y=0:064x + 0:032. (i) Can we estimate Fe in a sample with concentration 0-200 mg/L? Explain. (ii) Determine the concentration of Fe in the unknown sample. [Given : The blank sample was measured for 25 times and the standard deviation of the mean value (i.e., 0-040) is 0-008] 6+4 A sample of petroleum distillate during Doctor Test is shaken with a faint yellow colour solution X. No change in colour is observed. Then some sulphur is added and the solution turns dark brown. This happens when Y species is present in a petroleum distillate. What are X and Y? 24+3 Calculate the resolution of two analytes, whose chromatographic peaks are separated by 4 min with bandwidth of each analyte as 0:5 min. 5 Describe how the ion-exchange capacity of an anion-exchange resin can be measured using standard NaOH, standard HCl or any other reagent. 10 In the thermogravimetric analysis (TGA) of 0-45 g of Ca(OH)2 sample, the losses in weight at different temperatures are as follows : (i) 0-025 g at 100 °C-150 °C (ii) 0-040 g at 500 °C-560 °C (iti) 0-023 g at 900 °C-950 °C What is the composition of calcium hydroxide in the sample? 10 SNCS-C-CMS/73 5 [ P.T.O. (c) 5. (a) (b) (c) 6. (a) Using the following data, find the difference between gross calorific value and net calorific value of a coal sample whose composition (by weight) is carbon = 85:0%, hydrogen = 10-29% and ash = 4:71%. Data : Mass of the coal sample fired in a bomb calorimeter = 1:5 g Mass of water taken in the calorimeter = 2500 g Mass equivalent of the calorimeter = 2750 g Rise in temperature in the calorimeter = 3:0 °C Specific heat of water = 1 cal/(g °C) Latent heat of condensation of steam = 540 cal/g Assume all correction factors to be negligible. 10 Interference filters are used as wavelength selectors. Sketch a_ typical interference filter and explain how interference filters provide narrow band of radiation. 10 An organic acid dissolved in 50 mL of water is equilibrated with 50 mL of ether. The distribution coefficient (Kp) is 50 and the dissociation constant (Kg) is 5:0x10~>. Calculate the distribution ratio (D), if the aqueous layer is at pH 3, pH 5 and pH 7. 10 How will Cu content in a brass sample be quantitatively analyzed volumetrically without interference from Zn present? Describe the method and steps involved in the analysis. 10 SECTION—B Predict the major product in the following reactions, and name the reactions : CONH i) = ? 1, —_—_—_—— KOH NaN3, H»SO (ii) ee ees sg CHCl 2+2 SNCS-C-CMS/73 6 = Identify the major products in the given reactions : Ca(BH. (iii) ,) (© Identify the major product (20) formed in the following reaction sequence and suggest a suitable mechanism for the conversion of X > : 2 Cw ] _ व्यप + —Nacn ہیں‎ yr N CH3COjH ૦૪૦૦૩ > Lae H 0‎ H Y 4 (d) Predict the reactants and identify the name of the reactions in the following : OH ) NaCN, EtOH مٹیم‎ 4 ¢ A+B ¬ 3» 1 t-BuOK, t-BuOH (i) C+D = = ০০2৮৮ 2+2 (e) Identify the major products A and B formed in the following reactions : 202 2 2 mCPBA 7 => 13 NaOH 2+2 SNCS-C-CMS/73 7 [ P.T.O. | (f) Predict the major products (A-C) formed (with appropriate stereochemistry, if any) in the following reaction sequence : 4 (g) The optically active compound (X) racemizes on heating. Explain the observation : See x (Optically active) 4 (h) In IR spectrum, the selected bands observed for the unknown amide having molecular formula C,H gNO are 3350, 3200, 2925, 1660 and 1420 cm}, Among the following, identify the amide that gives the observed bands and justify your answer : NH “Yr ~ on Oo fe) A B Cc 4 (i) Using Woodward-Fieser rule, calculate A», for the following compounds and arrange them in the order of increasing Amax : CH; CH GH A B c 4 () The unknown dihaloalkane gives a molecular ion peak at m/z= 128 with a relative intensity of 75. The relative intensities of M+2 and M+4 peaks are 100 and 25 respectively. Identify the halides present in the compound and justify your answer. 4 SNCS-C-CMS/73 8 7. (a) Predict the major products (A-C) formed (with appropriate stereochemistry, if any) in the following reaction sequence. Describe the mode of cyclization involved under thermal and photochemical conditions : heat hy heat. C) A B Cc 10 (b) (i) }H-NMR spectrum of bullvalene (X) shows a single signal at 54-22 ppm at 10 °C. Explain the observation : Bullvalene (X) (ii) Suggest a suitable reaction mechanism for the following reaction : fe} fe} Cl Ph UN UN Me Me (c) (i) Identify the product and provide the name and mechanism for the following reaction : CO,H Na, liq. NH3 —————_———> ? ROH 5 (ii) Predict the major products X and Y formed in the following reaction sequence. Suggest a suitable mechanism for the formation of X : (e) CO.Et NaOEt NaOH Awe? CO Et >X PH + - 2 EtOH H,0 5 heat SNCS-C-CMS/73 9 [PrO; 8. (a) (b) (c) In a solution, acetylacetone exhibits keto-enol tautomerism. The chemical shift (5 in ppm) and their intensity observed in the !H-NMR of acetylacetone in CDCl3 is given below. [O—H signal of the enol tautomer is not shown] 5 (in ppm) Intensity 5:52 360 3°61 90 2:24 270 2:04 2160 (j) Assign the signals to the corresponding hydrogen in the tautomers. (i) Calculate the ratio of keto-enol tautomers and identify the major tautomer present in the solution. 10 (i) Draw the n-molecular orbitals of 1,3-butadiene and arrange them in the order of their energy. Assign the HOMO and LUMO under thermal and photochemical conditions. 5 (ii) Arrange the following dienes in the increasing order of reactivity towards maleic anhydride. Explain your answer : ‘Bu Bu Bu 5 A B (6) () The major product formed on ethyl propionate with KOH in ethanol gives a strong C=O stretching frequency at 1745cm™! and 1725cm7™! in IR spectrum. Identify the major product and suggest the suitable mechanism. 5 (i) The unknown monoterpene on complete reductive ozonolysis with O3 and Me.2S gave equimolar mixture of formaldehyde, acetone, pyruvaldehyde and malondialdehyde. Draw the structure of all the products and deduce the structure of the monoterpene. 5 SNCS-C-CMS/73 10 9. (a) Draw the major products formed in the following reactions and describe the process involved : fe) OMe . Me 2 heat (i) + ———- WS OMe fe) | PhS. heat 3 ea (ii) | Y Q Z heat 10 MeO (b) (i) Among the following, identify the ionone that will give the peak at m/z= 136 in EI mass spectrum and explain your answer : a-ionone B-ionone 5 (ii) Draw the major products (A-C) formed (with appropriate stereochemistry, if any) in the following reaction sequence : fe) I Meo7P~—CO2Me DIBAL-H Ti(O'Pr)4 ender MeO (2 equiv.) (+)-DET NaH, THF THF ‘BuOOH 5 (c) Propose the mechanism for polymerization of alkene C2H, when treated with Ziegler-Natta catalyst. Predict the nature of conductivity of the formed polymer and justify your answer. 10 10. (a) An organic compound having molecular formula C,;9H,,0,4 gave the following spectral data : IR : Significant absorption bands at 2904, 1725, 1641, 1244 cm! 1H-NMR (400 MHz, CDCl3) : 5 423 (q, J=7:2 Hz, 4H), 2:06 (s, 6 H) and 1-29 (t, J =7:2 Hz, 6 H) 13C_NMR (100 MHz, CDCl) : § 165-7, 154-9, 124-8, 60:8, 23-1 and 14-1 EI-MS : Prominent peaks at m/z 99 and 155 Deduce the structure of the compound and explain the data. 10 SNCS-C-CMS/73 (b) (i) Suggest a suitable method for the synthesis of the following compound (Z) from cyclopentadiene : 10) Z (ii) Identify the major products (X-Z) formed in the following reaction sequence : BH, 7 Ph~ “ - H20 Z NaOH 5 (c) (i) Predict the major product in the given reaction with possible mechanism. Also mention the fast and slow steps in the mechanism : OH + CHCl, + 3KOH —> ? (ii) Identify the major product formed in the following reaction and explain the stereochemical outcome : kkk SNCS-C-CMS/73 12 26BS—240