Exam JEE Advance

1. The pair(s) of reagents that yield paramagnetic species are
(a) Na and excess of NH3
(b) K and excess of O2
(c) Cu and dilute HNO3
(d) O2 and 2-ethylanthraquinol                             
Ans (a,b,c)
2. In a galvanic cell, the salt bridge
(a) does not participate chemically in the reaction
(b) stops the diffusion of ions from one electrode to another
(c) is necessary for the occurrence of the cell reaction
(d) ensures mixing of the two electrolytic solutions          Ans (a)
3.  Upon heating with Cu2S, the reagent(s) that give copper metal are
(a) CuFeS2                                                          
(b) CuO
(c) Cu2O                                                              
(d) CuSO4                                                                           
Ans (b,c,d)
4.  Hydrogen bonding plays a central role in the following phenomena
(a) ice floats in water
(b) higher Lewis basicity of primary amines than the tertiary amines in the aqueous solution
(c) formic acid is more acidic than acetic acid
(d) dimerization of acetic acid in benzene                      
Ans (a,b,d)
5. The correct combination of names for isomeric alcohols with molecular formula C4H10O is/are
(a) tert-butanol and 2-methylpropan-2-ol
(b) tert-butanol and 1, 1-dimethylethan-1-ol
(c) n-butanol and butan-1-ol
(d) iso-butyl alcohol 2-methylpropan-1-ol                                                                                            
Ans (a,c,d)
6. The correct statement(s) for orthoboric acid are
(a) it behaves as a weak acid in water due to self ionization
(b) acidity of its aqueous solution increases upon addition of ethylene glycol
(c) it has a three dimensional structure due to hydrogen bonding
(d) it is a weak electrolyte in water                                                                                            Ans (b,d)
7. Let M be a 2 x 2 symmetric matrix with integer entries. Then, M is invertible, if
(a) the first column of M is the transpose of the second row of M
(b) the second row of M is the transpose of the first column of M
(c) M is a diagonal matrix with non-zero entries in the main diagonal
(d) the product of entries in the main diagonal of M is not the square of an integer                                         
Ans (c,d)
8.  A circle S passes through the point (0, 1) and is orthogonal to the circles (x - 1)2 + y2 = 16 and x2 + y2 = 1. Then,
(a) radius of S is 8
(b) radius of S is 7
(c) centre of S is (-7, 1)
(d) centre of S is (-8, 1)                                       
Ans (b,c)
9. Heater of an electric kettle is made of a wire of length L and diameter d. It takes 4 minutes to raise the temperature of 0.5 kg water by 40 K. This heater is replaced by a new heater having two wires of the same material, each of length L and diameter 2d. The way these wires are connected is given in the options. How much time in minutes will it take to raise temperature of the same amount of water by 40 K ?
(a) 4, if wires are in parallel
(b) 2, if wires are in series
(c) 1, if wires are in series
(d) 0.5, if wires are in parallel                                                                                         Ans (b,d)
10. Parallel rays of light of intensity I = 912 Wm-2 are incident on a spherical black body kept in surroundings of temperature
300 K. Take Stefan constant  = 5.7 x 10-8 Wm-2 K-4 and assume that the energy exchange with the surroundings is only through the radiation. The final steady state temperature of the black body is close to 
(a) 330 K                                                              
(b) 660 K
(c) 990 K                                                              
(d) 1550 K                                                                                           
Ans (a)
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