The number of electrons, neutrons and protons in a species are equal to 10, 8 and 8 respectively. The proper symbol of the species
A 600 W mercury lamp emits monochromatic radiation of wavelength 331.3 nm. How many photons are emitted from the lamp per second? (h = 6.626 x 10-34 Js; velocity of light = 3×108 ms-1).
1 × 1019
1 × 1022
1 × 1021
1 × 1023
The shortest wavelength in hydrogen spectrum of Lyman series when RH = 109678 cm-1 is
1002.7 Å
1215.67 Å
1127.30 Å
911.7 Å
Which of the following statements is false?
H2 molecule has 1σ bond
Acetylene molecule has 3σ bonds and 3Π bonds
HCl molecule has 1σ bond
Water molecule has 2σ bonds and two lone pairs
N2 and O2 are converted to monopositive cation and respectively. Which is incorrect?
In , the N-N bond weakened.
In the bond order increases
In paramagnetism decreases
becomes diamagnetic
D.
becomes diamagnetic
A netural molecule XF3 has a zero dipole moment. The element X is most likely
chlorine
boron
nitrogen
carbon
56 g of nitrogen and 96 g of oxygen are mixed isothermally and at a total pressure of 10 atm. The partial pressures of oxygen and nitrogen (in atm) are respectively
6,4
4,6
5,5
2,8
How much time (in hours) would it take to distribute one Avogadro number of wheat grains, if 1020 grains are distributed each second?
0.1673
1.673
16.73
167.3
The first () and second (ΔH2) ionisation enthalpies (in kJ mol-1) and the (ΔegH) electron gain enthalpy (in kJ mol-1) of the elements I, II, III, IV and V are given below
Element | ΔH1 | ΔH2 | ΔegH |
I | 520 | 7300 | -60 |
II | 419 | 3051 | -48 |
III | 1681 | 3374 | -328 |
IV | 2372 | 5251 | +48 |
The most reactive metal and the least reactive non-metal of these are respectively
I and IV
IV and II
II and IV
III and IV
Calculate the standard enthalpy change (in kJ mol-1) for the reaction
H2(g) + O2(g) → H2O2(g)
Given that bond enthalpies of H-H, O=O, O-H and O-O (in KJ mol-1) are respectively 438, 498, 464 and 138.
-130
-65
+130
-334