51. An increase in equivalent conductance of a strong electrolyte with dilution is mainly due to
(1) Increase in number of ions
(2) Increase in ionic mobility of ions
(3) 100% ionisation of electrolyte at normal dilution
(4) Increase in both i.e. number of ions and ionic mobility of ions
52. 25.3 g of sodium carbonate, Na2CO3 is dissolved in enough water to make 250 mL of solution. If sodium carbonate dissociates completely, molar concentration of sodium ion, Na+ and carbonate ions, CO32– are respectively (Molar mass of Na2CO3 = 106 g mol–1)
(1) 0.477 M and 0.477 M (2) 0.955 M and 1.910 M
(3) 1.910 M and 0.955 M (4) 1.90 M and 1.910 M
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53. Property of the alkaline earth metals that increase with their atomic number
(1) Electronegativity
(2) Solubility of their hydroxides in water
(3) Solubility of their sulphates in water
(4) Ionization energy
54. Which of the following pairs has the same size?
(1) Zn2+, Hf4+ (2) Fe2+, Ni2+
(3) Zr4+, Ti4+ (4) Zr4+, Hf4+
55. In a buffer solution containing equal concentration of B– and HB, the Kb for B– is 10–10. The pH of buffer solution is
(1) 4 (2) 10
(3) 7 (4) 6
56. An aqueous solution is 1.00 molal in KI. Which change will cause the vapour pressure of the solution to increase?
(1) Addition of water (2) Addition of NaCl
(3) Addition of Na2SO4 (4) Addition of 1.00 molal KI
57. What is [H+] in mol/L of a solution that is 0.20 M in CH3COONa and 0.10 M in CH3COOH? Ka for CH3COOH = 1.8 × 10–5.
(1) 9.0 × 10–6 (2) 3.5 × 10–4
(3) 1.1 × 10–5 (4) 1.8 × 10–5
58. For the reaction N2O5 (g) → 2NO2 (g) + ½ O2 (g)the value of rate of disappearance of N2O5 is given as 6.25 × 10–3mol L–1s–1. The rate of formation of NO2 and O2 is given respectively as:
(1) 1.25 × 10–2 mol L–1s–1 and 6.25 × 10–3 mol L–1s–1
(2) 6.25 × 10–3 mol L–1s–1 and 6.25 × 10–3 mol L–1s–1
(3) 1.25 × 10–2 mol L–1s–1 and 3.125 × 10–3 mol L–1s–1
(4) 6.25 × 10–3 mol L–1s–1 and 3.125 × 10–3 mol L–1s–1
59. Standard entropies of X2, Y2 and XY3 are 60, 40 and 50 JK–1mol–1 respectively. For the reaction ½ X2 + 3/2 Y2 → XY3 , ΔH= 30kJ to be at equilibrium, the temperature should be
(1) 500 K (2) 750 K
(3) 1000 K (4) 1250 K
60.
(1) rate = k[A][B]2 (2) rate = k[A]2[B]
(3) rate = k[A][B] (4) rate = k[A]2[B]2
61. For the reduction of silver ions with copper metal, the standard cell potential was found to be +0.46 V at 25°C. The value of standard Gibbs energy, ΔG0 will be (F = 96500 C mol–1)
(1) –98.0 kJ (2) –89.0 kJ
(3) –89.0 J (4) –44.5 kJ
62. Which one of the following species does not exist under normal conditions?
(1) Li2 (2) Be2+
(3) Be2 (4) B2
63. AB crystallizes in a body centred cubic lattice with edge length ‘a’ equal to 387 pm. The distance between two oppositively charged ions in the lattice is
(1) 300 pm (2) 335 pm
(3) 250 pm (4) 200 pm
64. For an endothermic reaction, energy of activation is Ea and enthalpy of reaction is ΔH (both of these in kJ/mol). Minimum value of Ea will be
(1) Equal to zero (2) Less than ΔH
(3) Equal to ΔH (4) More than ΔH