Multiple Choice QuestionsWhich one of the following characteristics is associated with adsorption?
ΔG, ΔH and ΔS all are negative
ΔG and ΔH are negative but ΔS is positive
ΔG and ΔS are negative but ΔH is positive
ΔG and ΔS are negative but ΔH is positive
A.
ΔG, ΔH and ΔS all are negative
Adsorption is a spontaneous process that occurs with the release of energy and decrease in the entropy of the substance. For a spontaneous process, ΔG must be negative,
ΔG = ΔH - T ΔS
As the process is exothermic and randomness of the molecule (entropy) decreases hence both ΔH and ΔS will be negative as well.
The electronic configuration of Eu (Atomic no.63), Gd (Atomic no. 64) and Tb (Atomic no. 65) are
[Xe]4f6 5d1 6s2, [Xe] 4f7 5d1 6s2 and [Xe] 4f9 6s2
[Xe] 4f6 5d1 6s2 , [Xe] 4f7 5d1 6s2 and [Xe] 4f8 5d1 6s2
[Xe] 4f7 6s2, [Xe] 4f7 5d1 6s2 and [Xe] 4f9 6s2
[Xe] 4f7 6s2, [Xe] 4f7 5d1 6s2 and [Xe] 4f9 6s2
C.
[Xe] 4f7 6s2, [Xe] 4f7 5d1 6s2 and [Xe] 4f9 6s2
Electronic configuration of 63Eu [europium ]
= [Xe] 4f7 6s2,
Electronic configuration of 64Gd [gadolinium ]
= [Xe] 4f7 5d1 6s2
Electronic configuration 65Tb [terbium]
= [Xe] 4f9 6s2
The correct thermodynamic conditions for the spontaneous reaction at all temperatures is
B.
ΔH< 0 and ΔS > 0According to the Gibbs-Helmholtz reaction for spontaneity as,
ΔG =ΔH-TΔS
For reaction to being spontaneous, ΔG must be negative.
For this ΔH should be negative ΔS should be positive.
therefore,
ΔHΔS >0.
The addition of a catalyst during a chemical reaction alters which of the following quantities ?
Internal energy
Enthalpy
Activation energy
Activation energy
C.
Activation energy
A catalyst is a substance which alters the reaction but itself remains unchanged in the chemical reaction. In a chemical reaction, it provides a new reaction path by the lowering the activation energy barrier.
Predict the correct order among the following.
long pair-lone pair> bond pair-bond pair> lone pair>bond pair
bond pair-bond pair> lone pair-bond pair > lone pair -lone pair
lone pair -bond pair > bond pair- bond pair> lone pair -lone pair
lone pair -bond pair > bond pair- bond pair> lone pair -lone pair
D.
lone pair -bond pair > bond pair- bond pair> lone pair -lone pair
According to the VSPER theory, a lone pair occupies more space than a bond pair, Hence when lone pair-lone pair interacts with each other they repel more and thus the correct order is:
lone pair - lone pair > lone pair-bond pair > bond pair -bond pair.
The pair of an electron in the given carbanion,
is present in which orbital?
sp3
sp2
sp
sp
C.
sp
Equal moles of hydrogen and oxygen gases are placed in a container with a pin-hole through which both can escape. What fraction of the oxygen escapes in the time required for one-half of the hydrogen to escape?
1/4
3/8
1/2
1/2
D.
1/2
we have given,
a number of moles of hydrogen and
that of oxygen are
not equal.
In which of the following options the order of arrangement does not agree with the variation of the property indicated against it?
B<C<N<O (increasing first ionisation enthalpy)
I<Br<Cl<F(increasing electron gain enthalpy)
Li<Na<K<Rb (increasing metallic radius)
Li<Na<K<Rb (increasing metallic radius)
B.
I<Br<Cl<F(increasing electron gain enthalpy)
The electron gain enthalpy is defined as the energy released when an electron is added to a neutral gaseous atom to convert it into a negative ion. Large negative values of electron gain enthalpy indicate that it is easier to add an electron to an atom to convert it into an anion, and hence large amount of energy is released. The electron gain enthalpies in halogens decreases in the order
Cl>F>Br>I
because as we proceed down a group because the size of the atom increases. Therefore the distance of the nucleus from the valence orbital (which accepts the additional electron) increases. Hence the force by which the additional electron is attracted by the nucleus also decreases and the electron gain enthalpies become less negative as we proceed down a group.
Two electrons occupying the same orbital are distinguished by
Magnetic quantum number
Azimuthal quantum number
Spin quantum number
Spin quantum number
C.
Spin quantum number
Two electrons occupying the same orbital has equal spin but the directions of their spin are opposite. Hence, spin quantum number, s(represented +1/2 and -1/2) distinguishes them.
Consider the molecules CH4, NH3 and H2O. Which of the given statement is false?
The H-O-H bond angle in H2O is larger than the H-C-H bond angle in CH4.
The H-O-H bond angle in H2O is smaller than the H-N-H bond angle in NH3.
The H-C-H bond angle in CH4 is larger than the H-N-H bond angle in NH3
The H-C-H bond angle in CH4 is larger than the H-N-H bond angle in NH3
A.
The H-O-H bond angle in H2O is larger than the H-C-H bond angle in CH4.
According to VBT: lone pair-lone pair repulsion is more than a bond pair -lone pair repulsion.
As the number of lone pair of electrons on central element increases, repulsion between that lone pair of electrons increases and therefore, bond angle decreases.
|
Molecules |
Bond angle |
|
CH4 (no lone pair of electrons) |
1090.5 |
|
NH3(one lone pair of electrons) |
107.50 |
|
H2O (two lone pair of electrons) |
104.450 |
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