The number of radial nodes of 3s and 2p orbitals respectively are

• 0, 2

• 2, 0

• 1, 2

• 2, 1

The basis of quantum mechanical model of an atom is

• angular momentum of electron

• quantum numbers

• dual nature of electron

• black body radiation

The number of elements present in the fourth period is

• 32

• 8

• 18

• 2

4.

Identify the correct set.

• Molecule	Hybridisation of central atom	Shape
  PCl5	dsp3	square pyramidal

• [Ni(CN)4]2-

  sp3

  tetrahedral

• SF6

  sp3d2

  octahedral

• IF3

  dsp3

  pyramidal

Which one of the following statements is correct?

• Hybrid orbitals do not form σ bonds.

• Lateral overlap of p-orbitals or p- and d-orbitals produces $\mathrm{\pi }$-bonds.

• The strength of bonds follows the order-

  σ_p-p < σ_s-s < $\mathrm{\pi }$_p-p

• s-orbitals do not form σ bonds.

The degree of ionization of 0.10 M lactic acid is 4.0%

The value of K_c is

• 1.66 × 10^-5

• 1.66 × 10^-4

• 1.66 × 10^-3

• 1.66 × 10^-2

The pH of a buffer solution made by mixing 25 mL of 0.02 M NH₄OH and 25 mL of 0.2 M NH₄Cl at 25° is pK_b of NH₄OH = 4.8)

• 5.8

• 8.2

• 4.8

• 3.8

For which one of the following reactions, the entropy change is positive?

• H₂ (g) + $\frac{1}{2}$O₂ (g) → H₂O (l)

• Na⁺ (g) + Cl^- (g) → NaCl (s)

• NaCl (l) → NaCl (s)

• H₂O (l) → H₂O (g)

Solution 'X' contains Na₂CO₃ and NaHCO₃, 20 mL of X when titrated using methyl orange indicator consumed 60 mL of 0.1 M HCl solution. In another experiment, 20 mL of X solution when titrated using phenolphthalein, consumed 20 mL of 0.1 M HCl solution. The concentrations (in mol L^-1) of Na₂CO₃ and NaHCO₃ in X are respectively

• 0.01, 0.02

• 0.1, 0.1

• 0.01, 0.01

• 0.1, 0.01

A compound absorbs light in the wavelength region 490-500 nm. Its complementary colour is

• red

• blue

• orange

• blue-green