Total number of antibonding electrons present in O2 will be
6
8
4
2
A.
6
Total number of antibonding electrons present in O2 is 6.
Maximum number of unpaired electrons are present in
Gd3+
Yb2+
Tb2+
Pm3+
A.
Gd3+
Maximum number of unpaired electrons are present in Gd3+. It has 7 unpaired electrons.
Yb2+ has no unpaired electrons.
Tb2+ has 5 unpaired electrons.
Pm3+ has 4 unpaired electrons.
Which of the following is most basic?
Al(OH)3
Cr(OH)3
La(OH)3
Fe(OH)3
C.
La(OH)3
La(OH)3 is the most basic as it has the largest atomic size. Al(OH)3 is amphoteric in nature.
K2Cr2O7 in acidic medium converts into
Cr2+
Cr3+
Cr4+
Cr5+
B.
Cr3+
K2Cr2O7 in acidic medium converts into Cr3+. Since it is an oxidising agent, it undergoes reduction, i.e. decrease in oxidation state.
Cr2O + 14H+ + 6e- 2Cr3+ + 7H2O
In BF3, the B - F bond length is 1.30Å, when BF3 is allowed to be treated with Me3N, it forms an adduct, Me3N BF3, the bond length of B - F in the adduct is
greater than 1.30 Å
smaller than 1.30 Å
equal to 1.30 Å
none of these
A.
greater than 1.30 Å
In BF3, there is back bonding in between fluorine and boron due to presence of p-orbital in boron. Back bonding imparts double bond characteristics.
As BF, forms adduct the back bonding is no longer present and thus double bond characteristic disappears. Hence, bond becomes a bit longer than earlier (1.30 Å).
Assertion : Bond dissociation energy is F2 > Cl2.
Reason : Cl2 has more electronic repulsion than F2.
If both assertion and reason are true and reason is the correct explanation of assertion.
If both assertion and reason are true but reason is not the correct explanation of assertion.
If assertion is true but reason is false.
If both assertion and reason are false.
D.
If both assertion and reason are false.
Bond dissociation energy is F2 < Cl2 because of relatively large electron-electron repulsion among the lone pairs in F2 molecule where they are much closer to each other
than in Cl2.
What will be the solubility product of AX3?
27S4
4S3
36S4
9S3
A.
27S4
AX3
Ksp = [A3+] [X-]3
= (S).(3S)3 = 27S4
A particle is moving 3 times faster than the speed of electron. If the ratio of wavelength of particle and electron is 1.8 x 10-4 then particle is
neutron
- particle
deuteron
tritium
A.
neutron
Given : = 1.8 10-4
and = 3
According to de-Brogile equation,
Actual mass of neutron is 1.67493 10-27 kg. Hence, the particle is neutron.
Which thermodynamic parameter is not a state function?
q at constant pressure
q at constant volume
W at adiabatic
W at isothermal
D.
W at isothermal
H and U are state functions but W and q are not state functions.
From the equation,
At constant pressure,
At constant volume,
At constant pressure,
so, it is a state function.
At constant volume, V = 0, U = qv
so, it is a state function.
Work done in any adiabatic process is state function.
U = q - W ( q = 0)
U = -W
Work done in isothermal process is not a state function.
W = -q ( T = 0, q 0)
Which of the following element has lowest melting point?
Cr
Fe
Ni
Cu
D.
Cu
Cu has lowest melting point because it has lowest enthalpy of atomisation (i.e., heat required to break the metal lattice to get free atoms) among the elements.
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