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
C.
18
For 4th period, n = 4
Orbitals being filled = 4s, 3d, 4p
Number of elements in the period = 2, 10, 6 = 18
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 -bonds.
The strength of bonds follows the order-
σp-p < σs-s < 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 Kc 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 pKb 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) + 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