Practice Questions

Q49.A battery is constructed of Cr and Na2Cr2O7 . The unbalanced chemical equation when such a battery discharges is following: Na2Cr2O7 + Cr + H+ →Cr3+ + H2O + Na+ If one Faraday of electricity is passed through the battery during the charging, the number of moles of Cr3+ removed from the solution is (1) 4 (2) 1 3 3 (3) 3 (4) 2 3 3

Q49.The activation energy for a reaction which doubles the rate when the temperature is raised from 298 K to 308 K is (1) 59.2 kJ mol−1 (2) 39.2 kJ mol−1 (3) 52.9 kJ mol−1 (4) 29.5 kJ mol−1

Q49.According to Freundlich adsorption isotherm, which of the following is correct ? (1) m x ∝P 0 (2) mx ∝p1 (3) x ∝p1/n (4) All the above are correct for different ranges of m pressure

Q49.For a reaction A → Products, a plot of log t1/2 versus log a0 is shown in the figure. If the initial concentration of A is represented by a0 , the order of the reaction is (1) one (2) zero (3) two (4) three

Q49.The ppm level of F− in a 500 g sample of a tooth paste containing 0.2 g F− is (1) 400 (2) 1000 (3) 250 (4) 200

Q50.Which method of purification is represented by the following equation: 523 K 1700 K Ti(s) + 2I2(g) ⟶TiI4(g) ⟶Ti(s) + 2I2(g) (1) zone refining (2) cupellation (3) Poling (4) Van Arkel

Q50.On addition of 1 mL of 10%NaCl solution to 10 mL gold sol in the presence of 0.025 g of starch, the coagulation is just prevented. Starch has gold number JEE Main 2012 (19 May Online) JEE Main Previous Year Paper (1) 2.5 (2) 25 (3) 0.25 (4) 0.025

Q50. K1, K2 and K3 are the equilibrium constants of the following reactions (I), (II) and (III) respectively: (I) N2 + 2O2 ⇌2NO2 (II) 2NO2 ⇌N2 + 2O2 (III) NO2 ⇌12 N2 + O2 The correct relation from the following is (1) K1 = 1 = 1 (2) K1 = 1 = 1 K2 K3 K2 (K3)2 (3) K1 = √K2 = K3 (4) K1 = 1 = K3 K2

Q50.Colloidal solutions can be purified by JEE Main 2012 (26 May Online) JEE Main Previous Year Paper (1) emulsification (2) electrodialysis (3) peptization (4) using Tyndall effect

Q50.In a chemical reaction A is converted into B. The rates of reaction, starting with initial concentrations of A as 2 × 10−3M and 1 × 10−3 M, are equal to 2.40 × 10−4Ms−1 and 0.60 × 10−4Ms−1 respectively. The order of reaction with respect to reactant A will be (1) 0 (2) 1.5 (3) 1 (4) 2

Q51.The substance used as froth stabilisers in forth-floatation process is (1) Potassium ethyl xanthate (2) Aniline (3) Sodium cyanide (4) Copper sulphate

Q51.Fog is a colloidal solution of (1) solid particles dispersed in gas (2) solid particles dispersed in a liquid (3) liquid particles dispersed in gas (4) gaseous particles dispersed in a liquid

Q51.The correct statement for both the processes of physisorption and chemisorption is JEE Main 2012 (12 May Online) JEE Main Previous Year Paper (1) both are endothermic (2) chemisorption is endothermic but physisorption is exothermic (3) both are exothermic (4) physisorption is endothermic but chemisorption is exothermic.

Q51.Iron exhibits +2 and +3 oxidation states. Which of the following statements about iron is incorrect? JEE Main 2012 (Offline) JEE Main Previous Year Paper (1) Ferrous oxide is more basic in nature than the (2) Ferrous compounds are relatively more ionic than ferric oxide. the corresponding ferric compounds (3) Ferrous compounds are less volatile than the (4) Ferrous compounds are more easily hydrolysed corresponding ferric compounds. than the corresponding ferric compounds.

Q51.Reaction rate between two substance A and B is expressed as following: rate = k[A]n[B]m If the concentration of A is doubled and concentration of B is made half of initial concentration, the ratio of the new rate to the earlier rate will be: (1) m + n (2) n −m (3) 1 (4) 2(n−m) 2(m+n)

Q52.In the electrolysis of alumina to obtain aluminium metal, cryolite is added mainly to (1) lower the melting point of alumina (2) dissolve alumina in molten cryolite (3) remove the impurities of alumina (4) increase the electrical conductivity

Q52.The number of S −S bonds in SO3, S2O2−3 S2O2−6 and S2O2−8 respectively are (1) 1, 0, 0, 1 (2) 1,0,1,0 (3) 0, 1, 1, 0 (4) 0, 1, 0, 1

Q52.If x is the mass of the gas adsorbed on mass m of the adsorbent at pressure p, Freundlich adsorption isotherm gives a straight line on plotting (1) x/m vs p (2) x/m vs 1/p (3) log x/m vs log p (4) log x/m vs p

Q52.Extraction of zinc from zinc blende is achieved by (1) roasting followed by self-reduction (2) electrolytic reduction (3) roasting followed by reduction with carbon (4) roasting followed by reduction with another metal

Q52.Which among the following will be named as dibromidobis (ethylene diamine)chromium(III) bromide? (1) [Cr(en)3]Br3 (2) [Cr(en)2Br2]Br (3) [Cr( en )Br4]− (4) [Cr(en)Br2]Br

Q53.The d-electron configurations of Cr2+, Mn2+, Fe2+ and Co2+ are d4, d5, d6 and d7 respectively. Which one of the following will exhibit the lowest paramagnetic behaviour? (Atomic no. Cr = 24, Mn = 25, Fe = 26, Co = 27 ). (1) [Co(H2O)6]2+ (2) [Cr(H2O)6]2+ (3) [Mn(H2O)6]2+ (4) [Fe(H2O)6]2+

Q53.Which of the following forms stable +4 oxidation state? (1) La(Z = 57) (2) Eu(Z = 63) (3) Ce(Z = 58) (4) Gd(Z = 64)

Q53.How many chiral compounds are possible on monochlorination of 2−methyl butane ? (1) 8 (2) 2 (3) 4 (4) 6

Q53.Magnetic moment of Gd3+ ion (Z = 64) is (1) 3.62 BM (2) 9.72BM (3) 7.9 BM (4) 10.60BM

Q53.Reagent used to convert allyl alcohol to acrolein is (1) MnO2 (2) H2O2 (3) OsO4 (4) KMnO4