AIPMT Chemistry 1995

aipmt–Past papers CHEMISTRY- UNSOLVED PAPER - 1995

SECTION – I (Total Marks : 50) Single Correct Answer Type There are five parts in this question. Four choices are given for each part and one of them is correct. Indicate you choice of the correct answer for each part in your answer-book by writing the letter (a), (b), (c) or (d) whichever is appropriate .

01 Problem The pH value of blood does not appreciably change by a small addition of an acid or a base, because the blood Can be easily coagulated Contains iron as a part of the molecule Is a body fluid Contains serum protein which acts as buffer.

Problem 02 The secondary structure of a protein refers to Regular folding patterns of contiguous portions of the polypeptide chain Three-dimensional structure, specially the bond between amino acid residues that are distant from each other in the polypeptide chain Mainly denatured proteins and structures of prosthetic group Liner sequence of amino acid residues in the polypeptide chain.

Problem 03 The oxidation of glucose is one of the most important reactions in a living cell. What is the number of ATP molecules generated in cells from one molecule of glucose? 28 38 12 18.

Problem 04 Which of the following statements about enzymes are true? Enzyme catalyse chemical reactions by lowering the activation energy Enzymes are highly specific both in binding chiral substrates and in catalyzing their reactions Enzymes lack in nucleophilic groups Pepsin is proteolytic enzyme.

Problem 05 The bakelite is prepared by the reaction between Phenol and formaldehyde Tetramehtylene glycol Urea and formaldehyde Ethylene glycol.

Problem 06 Which product is formed, when acetonitrile is hydrolysed partially with cold concentrated HCl? Methyl cyanide Acetic anhydrides Acetic acid Acetamide.

Problem 07 Which one of the following products is formed when adipic acid is heated? a. b. c. d.

Problem 08 The most suitable method of the separation of a 1 : 1 mixture of ortho-and para-nitrophenols is Crystallization Chromatography Distillation Sublimation.

Problem 09 The order reactivity of carbonyl compounds for nucleophilic addition is H2C=O > R2C=O > Ar2C=O > RCHO > . H2C=O > RCHO > ArCHO > R2C=O >Ar2C=O ArCHO > Ar2C = O > RCHO > R2C = O > H2C = O

Problem 10 In the reaction CH3CHO + HCN -> CH3CH(OH)CN, a chiral center is produced. This product is Dextrorotatory Racemic mixture Meso compound Laevorotatory .

Problem 11 The oxidation of toluene with CrO3 in the presence of (CH3CO)2O gives a product A, which on treatment with aqueous NaOH, produces C6H5COONa 2,4-diacetyl toluene C6H5CHO (C6H5CO)2O.

Problem 12 When 3, 3-dimethyl 2-butanol is heated with H2SO4, the major product obtained is 2, 3-dimethyl 2-butene cids and trans isomers of 2,3-dimethyl 2-butene 2, 3-dimethyl 1-butene 3,3-dimethy 1-butene.

Problem 13 The alkene R-CH=CH2 reacts readily with B2H6 and the product on oxidation with alkaline hydrogen peroxides produces a. b. c. R-CH2-CHO d. R-CH2-CH2-OH.

Problem 14 When aniline reacts with oil of bitter almonds (C6H5CHO) condensation takes place and benzal derivative is formed. This is known as Schiff’s base Benedict’s reagent Million’s base Schiff’s reagent.

Problem 15 In which of the following compound there is more than one kind of hybridization (sp, sp2, sp3) for carbon? CH2=CH-CH=CH2 H-C C-H CH3CH2CH2CH3 CH3-CH=CH-CH3.

Problem 16 The IUPAC name for CH3CH=CHCH2CHCH2COOH is 3-amino 5-heptenoic acid β-amino ρ-heptenoic acid 5-amino 2-heptenoic acid 5-amino hex-2-ene-carboxylic acid.

Problem 17 Amongst TiF62-,CoF63-,Cu2Cl2 and NiCl42-, which are the colourless species? (atomic number of Ti = 22, Co = 27, Cu = 29, Ni = 28) CoF63-and NiCl42- TiF62-and Cu2Cl2 Cu2Cl2 and NiCl42- TiF62- and CoF63-

Problem 18 The coordination number and oxidation state number of Cr in K3Cr(C2O4)3 are respectively 3 and + 3 3and 0 6 and + 3 4 and + 2.

Problem 19 The number of geometrical isomers for [Pt(Nh3)2Cl2], is 3 1 4 2

Problem 20 In metal carbonyl having general formula M(CO)x where M = meral, x = 4 and the metal is bonded to Carbon and oxygen C O tripe bond Oxygen Carbon.

Problem 21 The mercury is the only metal which is liquid at 00C. This is due to its High vapor pressure Weak metallic bond High ionization energy Both (b) and (c).

Problem 22 Aluminum (III) chloride forms a dimmer because aluminum Belongs to 3rd group Can have higher coordination number Cannot form a trimmer Has high ionization energy.

Problem 23 The solubility in water of sulphate down the Be group is Be > Mg > Ca > Sr > Ba. This is due to Decreasing lattice energy High heat of salvation for smaller ions like Be2+ Increases in melting points Increasing molecular weight.

Problem 24 The sodium is made by the electrolysis of a molten mixture of about 40% NaCl and 60% CaCl2 because Ca++ can displace Na from NaCl This mixture has a lower melting point than NaCl CaCl2 helps in conduction of electricity Ca++ can reduce NaCl to Na.

Problem 25 On heating one end of a place of metal, the other end becomes hot because of Energized electrons moving to the other end Minor perturbation in the energy of atoms Resistance of the metal Mobility of atoms in the metal.

Problem 26 Identify the correct statement Plaster of Paris can be obtained by hydration of gypsum Plaster of Paris is obtained by partial oxidation of gypsum Gypsum contains a lower percentage of calcium than plaster of Paris Gypsum is obtained by heating plaster of Paris.

Problem 27 The BCl3 is a planar molecule whereas NCl3 is pyramidal because Nitrogen atom is smaller than boron atom BCl3 has no lone pair but NCl3 has a lone pair of electrons B-Cl bond is more polar than N-CI bond N-Cl bond is more covalent than B-Cl bond

Problem 28 About 20 Km above the earth, there is an ozone layer. Which one of the following statements about ozone and ozone layer is true? It is beneficial to us as it stops U.V. radiation Conversion of O3 to O2 is an endothermic Ozone has a triatiomic linear molecule It is harmful as it stops useful radiation.

Problem 29 According to Raoult’ s law, the relative lowering of vapor pressure for a solution is equal to Mole fraction of solute Mole fraction of solvent Moles of solute Mole of solvent.

Problem 30 The oxide, which cannot act as a reducing agent, is CO2 ClO2 NO2 SO2.

Problem 31 Half-life for radioactive 14C is 5760 years. In how many years 200 mg of14C will be reduced to 25 mg ? 17280 years 23040 years 5760 years 11520 years.

Problem 32 If enthalpies of formation for C2H4(g), CO2(g) and H2O (l) at 250C and 1 atom pressure are 52, -394 and –286 kJ/mol respectively , then enthalpy of combustion of C2H4(g) will be + 14.2 kJ/mol + 1412 kJ/mol -141.2 kJ/mol -1412 kJ/mol

Problem 33 An electrochemical cell is set up as : Pt; H2 (1 atm)|HCl(0.1 M)|| CH3COOH (0.1M) |H2 (1 atm); Pt, The e.m.f. of this cell will not be zero, because Acids used in two compartments are different e.m.f. depends on molarities of acids used The temperature is constant pH of 0.1 M HCl & 0.1 M CH3COOH is not same

Problem 34 The pH value of a 10 M solution of HCl is Equal to 1 Equal to 2 Less than 0 Equal to 0.

Problem 35 A chemical reaction is catalyzed by a catalyst X . Hence X Reduces enthalpy of the reaction Does not affect equilibrium constant of reaction Decreases rate constant of the reaction Increases activation energy of the reaction

Problem 36 An ideal gas, obeying kinetic energy theory of gases can not be liquefied, because It solidifies before becoming a liquid Forces acting between its molecules are negligible Its critical temperature is above 00C Its molecules are relatively small in size .

Problem 37 Standard state Gibb’s free energy change for is omerizxation reaction cis-2-pentene trans-2-pentene is –3.67 kJ/mol at 400 K. If more trans-2-pentene is added to the reaction vessel, then Equilibrium remains unaffected Equilibrium is shifted in the forward direction More cis-2-pentene is formed Additional cis-2-pentene is formed .

Problem 38 For a reaction to occur spontaneously H must be negative S must be negative ( H - T S) must be negative ( H + T S) must be negative.

Problem 39 The solubility of AgCl will be minimum in 0.01 M CaCl2 Pure water 0.001AgNO3 0.01M NaCl

Problem 40 The concentration units, independent of temperature, would be Normality Weight volume percent Molality Molarity.

Problem 41 The dimensions of pressure are the same as that of Force per unit volume Energy per unit volume Force Energy.

Problem 42 In liquid- gas equilibrium, the pressure of vapours above the liquid is constant at Constant temperature Low temperature High temperature None of these

Problem 43 The number of moles of oxygen in one liter of air containing 21% oxygen by volume, under standard conditions , is 0.0093 mole 2.10 moles 0.186 mole 0.21 mole.

Problem 44 Uncertainty in position of an electron an electron (mass = 9.1 x 10-28 g) moving with a velocity of 3 x 104 cm/s accurate up to 0.001% will be (Use h/( ) in uncertainly expression where h = 6.626 x 10-27 erg-second) 5.76 cm 7.68 cm 1.93 cm 3.84 cm.

Problem 45 Which of the following species is paramagnetic ? CO2 CN- O22- NO.

Problem 46 The radius of hydrogen atom in the ground state is 0.53 Ǻ . The radius of Li2+ ion (atomic number = 3 ) in a similar state is 0.53 Ǻ 1.06 Ǻ 0.17 Ǻ 0.265 Ǻ.

Problem 47 The correct order of the O-O bond length in O2, H2O2 and O3 is O2 > H2O2 > O3 H2O2 > O3 > O2 O2 > O3 > H2O2 O3 > H2O2 > O2 .

Problem 48 The electronic configuration of an element is 1s2 2s2 2p23s23p2. What is the atomic number of the element , which is just below the above element in the periodic table ? 36 49 33 34.

Problem 49 After the emission of one α-particle followed by one β-particle from the atom of x92282 the number of neutrons in the atom will be 144 143 148 146.

Problem 50 The ground state electronic configuration of valence shell electrons in the nitrogen molecule (N2) is written as .Hence the bond order in nitrogen molecule is 2 3 0 1.

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AIPMT Chemistry 1995

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