Recent questions in JEEMAIN PAST PAPERS

On mixing a certian alkane with chlorine and irradiating it with ultraviolet light, it forms only one monochloroalkane. This alkane could be :

asked Dec 11, 2018 by pady_1

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Nylon threads are made of :

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The reaction of chloroform with alcoholic KOH and p-toluidine form :

asked Dec 11, 2018 by pady_1

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The internal energy change when a system goes from state A and B is $40\; k\; J/mol$ . If the system goes from A to B by a reversible path and returns to state A by an irreversible path, what would be the net change in internal energy ?

asked Dec 11, 2018 by pady_1

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Ethyl isocyanide on hydrolysis in acidic medium generates :

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Bottles containing $C_6H_5I$ and $C_6H_5CH_2I$ lost their original labels. They were labelled A and B for testing. A and B were separately taken in a test tube and boiled with NaOH solution. The end solution in each tube was made acidic with dilute $HNO_3$ and then some $AgNO_3$ solution was added. Substance B gave a yellow precipitate. Which one of the following statements is true for this experiment ?

asked Dec 11, 2018 by pady_1

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The reason for double helical structure of DNA is operation of :

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The substance not likely to contain $CaCO_3$ is :

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For making good quality mirrors, plates of float glass are used. These are obtained by floating molten glass over a liquid metal which does not solidify before glass. The metal used can be :

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Complete hydrolysis of cellulose gives :

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When rain is accompanied by a thunderstorm, the collected rain water will have a pH value :

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Which one of the following nitrates will leave behind a metal on strong heating ?

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During dehydration of alcohols to alkenes by heating with concentration $H_2SO_4$ the initiation step is :

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The solubilities of carbonates decrease down the magnesium group due to a decrease in :

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Butene - 1 may be converted to butane by reaction with :

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The correct order of increasing basic nature for the bases $NH_3, \; CH_3NH_2$ and $(CH_3)_2NH$ is :

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Which one of the following statements is not true ?

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In curing cement plasters water is sprinkled from time to time. This helps in :

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Several blocks of magnesium are fixed to the bottom of a ship to :

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1 answer

The half-life of a radioactive isotope is 3 h. If the initial mass of the isotope were 256 g, the mass of it remaining undecayed after 18 h would be :

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The radionuclide $_{90}^{234} Th$ undergoes two successive $\beta$ -decays followed by one- $\alpha$ -decay. The atomic number and the mass number respectively of the resulting radionuclide are :

asked Dec 11, 2018 by pady_1

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The radius of $La^{3+}$ (Atomic number of La = 57) is $1.06 \mathring{A}$ . Which one of the following given values will be closest to the radius of $Lu^{3+}$ (Atomic number of Lu = 71) ?

asked Dec 11, 2018 by pady_1

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One mole of the complex compound $Co(NH_3)_5Cl_3$ , gives 3 moles of ions on dissolution in water. One mole of the same complex reacts with two moles of $AgNO_3$ solution to yield two moles of $AgCl(s)$ . The structure of the complex is :

asked Dec 11, 2018 by pady_1

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Ammonia forms the complex ion $[Cu(NH_3)_4]^{2+}$ with copper ions in the alkaline solutions but not in acidic solutions. What is the reason for it ?

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In the co-ordination compound, $K_4[Ni(CN)_4]$ , the oxidation state of nickel is :

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What would happen when a solution of potassium chromate is treated with an excess of dilute nitric acid ?

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The number of d-electrons retained in $Fe^{2+}$ (At. no. Fe = 26) ions is :

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The substance used in Holmes signals of the ship is a mixture of :

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Concentrated hydrochloric acid when kept in open air sometimes produces a cloud of white fumes. The explanation for it is that :

asked Dec 11, 2018 by pady_1

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A red solid is insoluble in water. However it becomes soluble if some $KI$ is added to water. Heating the red solid in a test tube results in liberation of some violet coloured fumes and droplets of metal appear on the cooler parts of the test tube. The red solid is :

asked Dec 11, 2018 by pady_1

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Which one of the following is an atmospheric oxide ?

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Which one of the following substances has the highest proton affinity ?

asked Dec 11, 2018 by pady_1

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Standard reduction electrode potentials of three metals $A, \;B$ and $C$ are $+0.5 V, \; -3.0 V$ and $-1.2V$ respectively. The reducing power of these metals are:

asked Dec 11, 2018 by pady_1

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In the respect of the equation $k = Ae^{-E_a/RT}$ in chemical kinetics, which one of the following statement is correct ?

asked Dec 11, 2018 by pady_1

1 answer

Which one of the following characteristics is not correct for physical adsorption ?

asked Dec 11, 2018 by pady_1

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In an irreversible process taking place at constant T and P and in which only pressure-volume work is being done, the change in Gibbs free energy (dG) and change in entropy (dS), satisfy the criteria :

asked Dec 11, 2018 by pady_1

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For a cell reaction involving a two-electron change, the standard emf of the cell is found to be 0.295 V at $25^{\circ}$ . The equilibrium constant of the reaction at $25^{\circ}C$ will be :

asked Dec 11, 2018 by pady_1

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For the reaction system : $2NO(g) + O_2(g) \to 2NO_2 (g)$ volume is suddenly reduced to half its value by increasing the pressure on it. If the reaction is of first order with respect to $O_2$ and second order with respect to NO; the rate of reaction will :

asked Dec 11, 2018 by pady_1

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If liquids A and B form an ideal solution, the :

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A pressure cooker reduces cooking time for food because :

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The enthalpy change for a reaction does not depend upon the :

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If at 298 K the bond energies of $C-H$ , $C-C$ , $C=C$ and $H-H$ bonds are respectively $414, \; 347, \; 615$ and $435 \; k \; J \; mol^{-1}$ , the value of enthalpy change for the reaction $H_2C = CH_2(g) + H_2(g) \to H_3C - CH_3 (g)$ at 298 K will be :

asked Dec 11, 2018 by pady_1

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The correct relationship between free energy change in a reaction and the corresponding equilibrium constant $K_c$ is :

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25 mL of a solution of barium hydroxide on titration with 0.1 molar solution of hydrochloric acid gave a titre value of 35 mL. The molarity of barium hydroxide solution was :

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The rate law for a reaction between the substances A and B is given by rate = $k [A]^n [B]^m$ . On doubling the concentration of A and halving the concentration of B, the ratio of the new rate to the earlier rate of the reaction will be as:

asked Dec 11, 2018 by pady_1

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In a 0.2 molal aqueous solution of a weak acid HX, the degree of ionisation is 0.3. Taking $K_f$ for water as $1.85$ , the freezing point of the solution will be nearest to :

asked Dec 11, 2018 by pady_1

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For the redox reaction $Zn(s) + Cu^{2+} (0.1 M) \to Zn^{2+} (1M) + Cu(s)$ taking place in a cell, $E^{\circ}_{cell}$ is $1.10\; volt$ . $E_{cell}$ for the cell will be : $(2.303 \frac{RT}{F}= 0.0591 )$

asked Dec 11, 2018 by pady_1

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When during electrolysis of a solution of $AgNO_3,$ 9650 coulombs of charge pass through the electroplating bath, the mass of silver deposited on the cathode will be :

asked Dec 11, 2018 by pady_1

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The solubility in water of a sparingly soluble salt $AB_2$ is $1.0 \times 10^{-5} mol\;L^{-1}$ . Its solubility product number will be :

asked Dec 11, 2018 by pady_1

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For the reaction equilibrium, $N_2O_4 (g) \rightleftharpoons 2 NO(g)$ the concentrations of $N_2O_4$ and $NO_2$ at equilibrium are $4.8 \times 10^{-2}$ and $1.2 \times 10^{-2} mol L^{-1}$ respectively. The value of $K_c$ for the reaction is :

asked Dec 11, 2018 by pady_1

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