IIT-JAM Chemistry Paper-2007

Transcription

1 IIT-JAM Chemistry Paper-007 CEMISTRY Instruction: Q.1-30 (bjective questions) carry three marks each and Q (Subjective questions) carry fifteen marks each. 1. The compound, which (i) Reacts rapidly with acetyl chloride (ii) Does not react with, 4-dinitrophenylhydrazine and (iii) Does not form a yellow precipitate with excess of iodine in aqueous alkali is Acetone (b) Diethyl ether (c) -methyl--propanol (d) Ethanol C C. C 1 C The given compounds 1 and are Identical (b) Diastereomeric (c) Enantiomeric (d) Constitutionally isomeric. 3. The correct order of dipole moments of the following componds is: 1. C3CCC. C3C CC 3. C3CC C 1 3 (b) 3 1 (c) 3 1 (d) Which one of the following compounds gives positive test for both nitrogen and halogen with its Lassaigne s extract? C3N. (b) N. (c) N4 (d) NN. 5. Which one of the following compounds is optically active? (1) () (3) (4) 1 (b) (c) 3 (d) 4 6. The compounds that react with aqueous NaC 3 to release C are N N C (1) () (3) (4) 1 and3 (b) and 4 (c) and 3 (d) 1 and 4 1

2 CEMISTRY 7. The complementary strand of DNA for the following single stranded DNA sequence, 5' A T C A T G C 3' is: 5' A T C A T G C 3' (b) 5' T A G T A C G 3' (c) 5' G C A T G A T 3' (d) 5' C G T A C T A 3' 8. The value of n for the following molecule according to uckel s rule is: 16 (b) 4 (c) 3 (d) Which one of the following compounds reacts with nitrous acid to give the product [P]? [P] = (b) N N (c) (d) N N 10. The main product obtained in the following reaction is: 1. MeMgBr/dry ether. + / [?] (b) (c) (d) 11. For a reaction with rate equation dc/dt = kc, C 0 and C are the concentrations of the reactant at time 0 and t respectively. If 10 minutes were required for C 0 to become C 0 /, the time required for C 0 to become C 0 /4 is: 10 min (b) 0 min (c) 30 min (d) 40 min.

3 CEMISTRY 1. For a cyclic process performed by an ideal gas, changes in some thermodynamic functions are zero. Indicate the set in which all the functions are zero. w, E,, G (b) q, S,, A (c) q, E, S, G (d) E, S,, A 13. The plot of Gibb s free energy G and the extent of a reaction is given below for the reaction A B. If A and B are the chemical potentials of A and B respectively, the INCRRECT statement is: Gibb s free energy X Y Z 0 Extent of reaction At point X, A B (b) At point Y, G 0 (c) At point Z, A B (d) At equilibrium, the composition of the reaction mixture can be identified. 14. The overlap between the atomic orbitals sketched below is: Z + Y Z + Y + X + X Positive (b) Negative (c) Zero (d) No overalp 15. The p of a M solution of a weak acid A is 4.0. The acid dissociation constant K a is: (b) (c) (d) The normalisation constant A for the wavefunction im Ae where 0 is: 1 (b) (c) (d) The standard potential of a Daniel cell is V and the equilibrium constant for the cell reaction is It can be concluded that Zinc oxidises copper (b) Displacement of copper by zinc goes to near completion. (c) Copper oxidises zinc (d) Displacement of zinc by copper goes to completion. 3

4 CEMISTRY 18. Which one of the following figures, showing kinetic energy of the ejected electron versus the frequency (v) of the incident photon, represents the Einstein s photoelectric effect? K.E. (J) 1 v(s ) (b) K.E. (J) 1 v(s ) 19. An aqueous solution containing 0.01 M Fe 3 and 0.06 M 4 has the same ionic strength as a solution of 0.09 M Na (b) 0.04 M CuS 4 (c) 0.06 M CuS 4 (d) 0.03 M 3 P 4. (c) K.E. (J) 0. Which one of the following species is the conjugate base of? 0 1 v(s ) (b) (c) (d) 1. The solid-liquid phase diagram for the Mg-Zn system is shown in the figure below where the vertical line at X(Mg) = 0.33 represents the formation of a congruent melting compound MgZn. The figure is divided into seven regions depending upon the physical state of the system. The composition of the region #6 represents. (d) 3 K.E. (J) 0 1 v(s ) # #3 #5 #1 #7 300 #4 # Zn x(mg) Mg Single phase of a solution of Mg and Zn (b) Two phase region between the solid Zn and solid MgZn. (c) Two phase region between the liquid and solid MgZn. (d) Two phase region between solid Mg and solid MgZn.. In the extraction of metals from their ores, which one of the following reduction methods can bring about a nonspontaneous reduction? Electrolytic reduction (b) Reduction by carbon (c) Reduction by another metal (d) Reduction by hydrogen. 3. The correct order of the ionic radii is: 3 4 ln Sn Sr Rb (b) 4 3 Sn ln Sr Rb (c) 3 4 Rb ln Sr Sn (d) 3 4 Rb Sr ln Sn 4

5 CEMISTRY 4. The correct valence shell electronic configuration of the element with atomic number is 4 Ar4s 3d (b) Ar3d (c) Ar3d 4s (d) Ar4s 4p 5. The ligand with only sigma bonding character is: CN (b) C 3 (c) C (d) N 6. Which one of the following species is NT isoelectronic with C? N (b) CN (c) N (d) 7. During witting reaction, a phosphorus yield gets converted to R3P (b) R3P 0 (c) R3P (d) R P PR 8. Which of the following reactions does NT give 3 P 4? Ca P S (b) P (c) P5 (d) P4S The ionic radii of Ca + and F are 100 pm and 133 pm respectively. The coordination number of Ca + in the ionic solid will be 8 (b) 6 (c) 4 (d) 30. The shape of C 3 ion is: trigonal planar (b) tetrahedral (c) trigonal pyramidal (d) linear. 31. Identify reagent (P) and write the structure of products (Q, S and T) in the following [P] 1. KMn 4. NaI 4 [Q] C Na. + [R]C 11 1 [T] Na 1. C 3 MgBr (excess). Br [S] C Br Identify the structures of the intermediate compouds Q, R and S. Show the transformation for each step 5

6 CEMISTRY 3. For the following scheme of transforamations, draw the structures of A, B, C and D. C phenylhydrazine (3 eq) [A] benzaldehyde (excess) + [B] C acid catalysed rearrangement [D] Br / [C] I 4 (b) Complete hydrolysis of a pentapeptide with 6 N at 110ºC in a sealed tube gave equivalents of glycine, one equivalent each of tyrosine, leucine and phenylalanine. Reaction of the pentapeptide with Sanger s reagent (, 4-dinitrofluorobenzene, DNFB) and subsequent hydrolysis gave the DNFB derivative of tyrosine. Chymotrypsin cleavages of this peptide yielded tyrosine, leucine and a tripeptid. Deduce the sequence of the pentapeptide. 33. Complete the following reactions with appropriate structures for E, F, G, and I. CEt NaN / [E] Zn/Ac [F] [F] + C Et heat [G] (b) alkaline KMn 4 [] heat, acetophenone N 34. Account for the following transformation with an appropriate mechanism. Give the structure of the offmann exhaustive methylation product of 1, -dihydro derivative of [X]. Me Me N P 5 (b) The optically pure ester [J] is hydrolysed in aqueous acetic acid to form a racemic mixture of cis-4, 4- dimethyl--acetoxycyclopentanol [K]. Give a mechanistic explanation to account for the formation of [K] and the observed change in the optical activity. 35. M is a first row transition metal. M on treatment with aqueous ammonia gives a blue coloured solution Me Me [I] [X] N 6

7 of complex N. A solution of M also gives a bright red prcipitate of complex with ethanoic dimethylglyoxime. (i) Identify M and draw the structure of. (ii) Determine the hydridisation of M in complex N. (iii) Identify the paramagnetic complex. (b) Cr 3 6 stabilisation energy of this complex in kj/mol. CEMISTRY gave an absorption at 08 kj/mol which corresponds to 0. Calculate the crystal field 36. Consider the ethers 3SiSi 3 and 3CC 3. (i) Which ether has more lewis base character? (ii) Which angle [Si Si and C C] is greater? Justify your answer. (b) Starting from Si, show how the following polymer is prepared industrially? C 3 Si C A solution of metal ion M n when treated with S gas gives a black precipitate A. Precipitate A dissolved in hot concentrated nitric acid to give B along with elemental sulfur. The metal ion solution also gives a white precipitate C with an excess of KI. Write the chemical formulae of A, B, and C (b) Why are potassium permanganate solutions unstable in the presence of Mn + ions? In the quantitative estimation of iron present in iron ores dissolved in dilute, titrations with dichromate are preferred over titrations with permanganate. Rationalise. 38. Al 6 and Al Me 6 are dimeric in gas phase. Draw their structures. Which compound has more Lewis acid character? Explain. (b) Arrange the halides Sn, Pb,Si in increasing order of their stability. Give reasons for your answer. 39. Acidification of an aqueous solution of yellow sodium chromate gives an orange coloured A. A compound solution of A on treatment with concentrated S 4 gives a bright orange solid B. Compound A in the presence of concentrated S 4 reacts with anion C to give a deep red coloured liquid. Identify A, B and C. (b) P undergoes an emission to give element X followed by a emission to give element Y. (i) Write the valence shell electronic configuration of Y. (ii) Indicate the groups of the periodic table to which X and Y belong. 40. When an ideal monoatomic gas is expanded from 1.5 bar, 4.8 L and 98 K into an evacuated container, the final volume becomes 49.6 L. Calculate, S and G for the process. (b) The Maxwell distribution function for the distribution of speeds of molecules in gaseous systems is given by 3 m mc f c 4 c exp kt kt kt Show that the most probable speed, cmps m 41. At 600 K and 00 bar, a 1:3 (molar ratio) mixture of A and B react to form an equilibrium mixture 1 7

8 CEMISTRY containing x 0.60 AB3. Assuming ideal gas behaviour, calculate K p for the reaction A g 3B g AB g (b) A 50 ml 0.05 M solution of Fe(II) is titrated with 0.05 M solution of Ce(IV) in the presence of dilute S 4 at 5ºC. Calculate the equivalence point potential and the equilibrium constant K in terms of log K. 0 0 E V, E V Fe /Fe Ce /Ce 4. The vapour pressure of D at 0 ºC is 745 mm g. When 15 g of a non-volatile compound is dissolved in 00 g of D, the pressure changes to 730 mm g. Assuming the applicability of Raoult s law, calculate the molecular weight of the compound. (b) An enzyme following Michaelis-Menten kinetics was found to have highest activity at 37ºC and p 7.0. If the maximum velocity Vmax E 0.4 nm, calculate the turnover frequency. for this enzyme was mol L 1 s 1 with an initial enzyme concentration 43. Consider the 4 electrons in cyclobutadiene to be free particles in a -dimensional square box of length Å. Calculate the wavelength of the electronic transition from the highest occupied molecular orbital (M) to the lowest unoccupied molecular orbital (LUM). Also write down the normalised wavefunctions for the occupied degenerate states. (b) The reaction k 1 k 1 cis trans is first order in both directions. At 5ºC, the equilibrium constant (K) of this reaction is If mol. dm 3 of cis-isomer is allowed to equilibrate, calculate the equilibrium concentration of each isomer. 44. With i, j and k as the unit vectors along, X, Y, Z axes, express the vector, P 1 P in the given figure in terms of the coordinate of P 1 and P. Also determine the dot products of the unit vectors, i, j, k. Z ^ k P (x, y, z ) X ^ i ^ j Y P 1(x 1, y 1, z 1) (b) Deduce whether the matrices A and B commute or not A B