QP-CGSMain-24-CHEMISTRY-PAPER-I-240624

vombined Geo-Scientist (Main) SGSE-P-CMS Examination, 2024 CHEMISTRY PAPER—I Time Allowed : Three Hours Maximum Marks : 200 QUESTION PAPER SPECIFIC INSTRUCTIONS Please read each of the following instructions carefully before attempting questions There are ELEVEN questions divided under SIX Sections. Candidate has to attempt SIX questions in all. The ONLY question in Section—A is compulsory. Out of the remaining TEN questions, the candidate has to attempt FIVE, choosing ONE from each of the other Sections B, C, D, E and F. 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. SGSE-P-CMS/67 1 [P20 SECTION—A ( Compulsory Section ) Answer all of the following : 5*x10=50 1. (a) Match the following : 5 (i) Dolomite 1. Alumina (i) Corundum 2. MgCO, -CaCO3 (iii) Sphalerite 3. CuFeS, (iv) Silicon 4. ZnS (v) Chalcopyrite 5. Semiconductor (b) The observed magnetic moment for K3[TiF,] is 1-70 pg. (i) Calculate p (spin only) for this complex. (ii) Why is there a difference between calculated and observed values? 5 (c) Match the following : 5 Titrations involving A (i) Strong acid vs. Weak base (ii) Weak acid vs. Strong base (iii) Strong acid vs. Strong base (iv) Weak acid vs. Weak base (v) Redox reactions 1 2 3. 4 5 B Methylene blue (pKg= 3-8) Bromothymol blue (pKg= 7-2) No indicator Phenolphthalein (pK, = 9-3) Methyl orange (pKg= 3-5) (d) A sample of slag from a blast furnace is analyzed for SiO, by decomposing a 0:5003 g sample with HCl leaving a residue with a mass of 0:1414 g. After treating with HF and H,SO,, and evaporating the volatile SiF,, a residue with a mass of 0-0183 g remains. Determine the % w/w SiO, in the sample. 5 (e) Given that the standard electrode potentials for the reactions 2Fe2* (aq) = 2Fe3* (aq) + 2e7 H,0, +2H* (aq) + 2e7 = 2H, (i) Oo. (ii) are -O-77V and 1-77 V respectively. Determine whether the oxidation of Fe2* to Fe°* is spontaneous or SGSE-P-CMS/67 not. () MnO; is a stronger oxidizing agent than ReO. Explain and relate the oxidizing abilities of these ions with the relative positions of their charge-transfer absorptions. 5 (g) What pH is better for the effective use of CN” as a masking agent? Explain the reason for this pH dependency. 5 (h) The complex [Fe2(Cp)2(CO)4] has one strong IR band at 1800 cm7! and other bands appeared at ~ 1980 cm! and 2020 cm”! for CO. Account for each band with proper reason. 5 (i) Which of the curves represent nuclear decay? Justify your answer with mathematical logic : 5 = a is) = 2 5 8 < Time, h @) Explain why stable and readily isolable carbonyl complexes are unknown for the lanthanoids. 5 SECTION—B Attempt any one question 2. (a) (i) Differentiate between fluorite and antifluorite. (ii) Differentiate between Schottky defect and Frenkel defect. (iti) Differentiate between spinel and inverse spinel. 5+5+5=15 (b) Discuss each of the following observations : 10 () The [CoC] 4]?~ ion is a regular tetrahedron but [CuCl,]*~ has a flattened tetrahedral structure. (ii) The electronic spectrum of [CoF,]*~ contains two bands with maxima at 11500 cm™! and 14500 cm”!. (c) What is polymorphism in crystals? Give an example. 5 SGSE-P-CMS/67 3 [ P.T.O. 3. (a) () () 4. (a) (b) (Q) The titration curve for a weak acid vs. strong base (NaOH) has the following shape : (4) pul (3) (2) (1) Vol. of OH” added ——> () Identify the weak acid : I. CH3COOH (K, =1-69x1075) Il. HCN (K, =5x107!°) Ill. Benzoic acid (K, =6-3x107) IV. Pyridinium ion (K, =5-9 x1076) (i) Explain the process and species involved in the regions marked as (1), (2), (3) and (4) that contribute to the pH at near regions. What are the general criteria of choosing a suitable indicator for a given volumetric titration? Give the salient features of estimation of sodium carbonate and bicarbonate mixtures by acidimetry. Which two acid-base indicators are used and why? SECTION—C Attempt any one question Oxyhemoglobin is bright red, whereas deoxyhemoglobin is purple. Explain the difference in colour qualitatively. Given the reactants PPh3;, NH; and [Ptcl,]?", propose efficient routes to both cis and trans [PtCl,(NH3)(PPh3)]. Iron(II) oxide, FeO crystal has a cubic structure and each edge of the unit cell is 5-0A. Taking density of the oxide as 4-0 gem, calculate the number of Fe2* and O?~ ions present in each unit cell. SGSE-P-CMS/67 4 15 10 10 10 10 5. (a) The compound [Ni3(C2H5)3(CO),] has a single CO stretching absorption at 1761cm~}. The IR data indicate that all C sHs ligands are pentahapto and probably in identical environments. () On the basis of these data, propose a structure. (ti) Does the electron count for each metal in the structure agree with the 18e° rule? 10 (b) Identify the required particles to produce the listed product nuclei : 10 28a; 1451 28 1341 27A) 31 ise 35 17C1 (c) An ore containing magnetite, Fe,0, was analyzed by dissolving a 1-500 g sample in conc. HCl giving a mixture of Fe?* and Fe**. After adding HNO, to oxidize any Fe** to Fe°*, the resulting solution was diluted with water and Fe3+ precipitated as Fe(OH), by adding NH3. After filtering and rinsing, the residue was ignited giving 0- 8525 g of pure Fe203. Calculate the % w/w Fe304 in the solution. [Given : FW of Fe,03 =159-69g/mol and FW of Fe30, = 231-54 g/mol] 10 SECTION—D Attempt any one question 6. (a) A thermogram was recorded for calcium oxalate monohydrate, CaC,0,-H,0. The original sample weighed 24-60 mg and was heated from room temperature to 1000°C at a rate of 5°C/min. The following changes in mass and corresponding temperature ranges were observed : Loss of 3:03 mg from 100-250 °C Loss of 4:72 mg from 400-500 °C Loss of 7-41 mg from 700-850 °C Determine the solid residue at each step of the thermal decomposition. 15 SGSE-P-CMS/67 5 [PePO: (b) (c) (a) (b) (¢) (a) Match the following : (i) Cupferron 1. Co?* (ii) Cupron 2. Ni2* (iii) 1-Nitroso-2-naphthol 3. aAls* (iv) Dimethylglyoxime 4. Cu?+ (v) 8-Hydroxyquinoline 5. FeSt 6. Pb** 7. Cr3* Discuss the following observations : (i) AH? for the formation of [Ln(EDTA)(OH,),]” (x =2 or 3) in aqueous solution is nearly constant for all Ln and is almost zero. (ii) Many actinoid oxides are non-stoichiometric but few lanthanoid oxides are. Explain the terms oxidative addition and reductive elimination in the hydrogenation reactions and how the coordination numbers of the metal atom alter with an example. (i) Draw the two isomeric forms of Co(CO)g. (ii) Show the cluster structure of Ir,(CO),2 metal-metal bonds. Ordinary bottle glass appears nearly colourless when viewed through the wall of the bottle but visibly coloured (green) when viewed from the end so that light has a long path through the glass. The colour is associated with the presence of Fe?* in the silicate matrix. Explain this observation. SECTION—E Attempt any one question Complete the following by giving the missing part on the right or left hand side of the equations and also identify their applications in daily life or industry : () 2? ——+ PbSO, +2e7 (i) PbO, +4H* +SO2- +2e° ——> ?? (iii) 6CO,+6H,0 —™+ 7? (iv). 9? ——» Cu SGSE-P-CMS/67 6 10 10 10 10 15 (b) Following are the standard redox potentials for the reactions in aqueous media : 282” + € +1-98V 118 + 2 = Mg -2-37V 14 +€ =Li -3-04V 08 + 207 © -2-87V Nat+e =Na -2-71V Arrange the above metals in the order of their increasing reducing power. 5 (c) Establish that the end point in a redox reaction occurs when 0-05916 সলাত ঢ় 9. (a) Calculate the activity (in dpy) due 151 1-00 kg of carbon found in a living specimen. The abundance of 110 in a carbon sample present-day specimen is 1.3 ×10-12 (1/2 of 140 is 5730 ¥, ? = 6-023 ×10 23 atoms/mole, At. mass of carbon = 12.01 1 ). 10 (b) Identify the missing part in the following nuclear reactions : 5 711 + ? - 108 + dn ? + + 126 + ‎ 8 + $He 49] + gn ¬ 191 + 4221 + 4‎ ? + gn ( Explain the relation between elementary separation factor, and enrichment factor, in terms of abundance of a particular isotope in a mixture during the 10 separation. 3) A sample of radioactive isotope with 0/2 of 1600 y has an activity of 20 mCi 1/2 (Ci =curie). How long it would take the activity to be reduced to almost 1mCi (= 1-25 mCi)? SGSE-P-CMS/67 7 [ P.T.O. SECTION—F Attempt any one question 10. (a) The EDTA titration of mixtures of Ca?* and Mg2* can be followed thermometrically. Sketch the thermometric titration curve for a mixture of 5-00 x1073 M Ca?* with 5-00 x10-9 M Mg2* with 0-0100 M EDTA. The heats of formation for CaY?- and MgY?~ are respectively -23-9 kJ/mol and -23-0 kJ/mol. (Given : log K, for Ca?* -EDTA complex = 10-69 and log K, for Mg?*-EDTA complex = 8-79) 10 (b) Show that F~ is an effective masking agent in preventing a reaction of Al°* with EDTA. Assume that only significant forms of fluoride and EDTA are F~ and Y*~. (Given : (i) logK, =6-11, logK,=5-01, logK3 =3-88, logK, =3-00, log K, =1-4, logK, =0-4 for the complexes between Al$* and F™ and (ii) log K for the complex between EDTA and Al°* =16-3) 10 (c) (i) Write the following ligand-exchange reactions : 1. [CofH,0)¢]°* + 6NH; > 2. [CofH20),¢]°* + 3en > (ii) Which of the reactions should have a larger AS°? (iii) Given that Co—N bond length is approximately same in both complexes. Which reaction will have a larger equilibrium constant? Explain your choice. 10 11. (a) Calcium in powdered milk is determined by ashing a 1:50 g sample and then titrating calcium with EDTA solution, 12:1 mL being required. EDTA was standardized by titrating 10-0 mL of a zinc solution prepared by dissolving 0-632 g zinc metal in acid and diluting to 1 L (10-8 mL EDTA is required for titration). What is the concentration of calcium in the powdered milk in parts per million? 10 (b) Give the trends in the stability of higher oxidation states in the first row d-block metal compounds. 10 (c) (i) Explain why isostructural HfO, and ZrO, have densities of 9-68 g cm ° and 5-73 gcm’® respectively. (ii) Why are high coordination numbers not usual for first row d-block elements? 10 kkk SGSE-P-CMS/67 8 SB24—288