What is the correct order of spin only magnetic moment (in BM) of Mn²⁺, Cr²⁺ and V²⁺ ?

• Mn²⁺ > V²⁺ > Cr²⁺

• V²⁺ > Cr²⁺ > Mn²⁺

• Mn²⁺ > Cr²⁺ > V²⁺

• Cr²⁺ > V²⁺ > Mn²⁺ 

A molecule (X) has 

(i) four sigma (σ) bonds formed by the overlap of sp² and s orbitals

(ii) one sigma (σ) bond formed by sp² and sp² orbitals and 

(iii) one $\mathrm{\pi }$ bond formed by p_x and p_z orbitals.

Which of the following is X?

• C₂H₆

• C₂H₃Cl

• C₂H₂Cl₂

• C₂H₄

Which of the following is not correct?

• 3O₂ $\underset{\mathrm{discharge}}{\overset{\mathrm{silent} \mathrm{electric}}{\rightleftarrows }}$ 2O₃ ; $∆$H = -284.5 kJ

• Ozone undergoes addition reaction with unsaturated carbon compounds

• Sodium thuosulphate reacts with I₂ to form sodium tetrathionate and sodium iodide.

• Ozone oxidises lead sulphide to lead sulphate.

4.

Observe the following statements :

I. The physical and chemical properties of elements are periodic functions of their electronic configuration.

II. Electronegativity of fluorine is less than the electronegativity of chlorine.

III. Electropositive nature decreases from top to bottom in a group.

The correct answer is :

• I, II and III are correct

• only I is correct

• only I and II is correct

• only II and III are correct

The uncertainties in the velocities of two particles A and B are 0.05 and 0.02 m/s^-1 respectively. The mass of B is five times to that of mass A. What is the ratio of uncertainities $\left(\frac{∆{\mathrm{x}}_{\mathrm{A}}}{∆{\mathrm{x}}_{\mathrm{B}}}\right)$ in their positions?

• 2

• 0.25

• 4

• 1

The energy of a photon is 3 × 10^-12 ergs. What is its wavelength in nm ?

(h = 6.62 × 10^-27 ergs ; c = 3 × 10¹⁰ cm/s)

• 662

• 1324

• 66.2

• 6.62

Which of the following set of variables give a straight line with a negative slope when plotted? (P = vapour pressure ; T = Temperature in K)

• y - axis	x - axis
  P	T

• log10 P

  T

• log10 P

  $\frac{1}{\mathrm{T}}$

• log10 P

  log10 $\frac{1}{\mathrm{T}}$

Which of the following is not a characteristic property of chemical equilibrium ?

• Rate of forward reaction is equal to rate of backward reaction at equilibrium.

• After reaching the chemical equilibrium, the concentrations of reactants and products remain unchanged with time.

• For A (g) $\rightleftharpoons$ B (g), K_c is 10^-2. If this reaction is carried out in the presence of catalyst, the value of K_c decreases.

• After reaching the equilibrium, both forward and backward reactions continue to take place.

The concentration of oxalic acid is 'x' mol L^-1. 40 mL of this solution reacts with 16 mL of 0.05 M acidified KMnO₄. What is the pH of 'x' M oxalic acid solution ? (Assume that oxalic acid dissociates completely)

• 1.3

• 1.699

• 1

• 2

Which of the following is not correct ?

• Nuclei of atoms participate in nuclear reactions

• ₂₀Ca⁴⁰ and ₁₈Ar⁴⁰ are isotones

• 1 amu of mass defect is approximately equal to 931.5 MeV.

• Uranium (U²³⁸) series is known as (4n + 2) series.