NIOS TMA ASSIGNMENT CHEMISTRY (313) SOLVED PAPER – (2024-25)| SENIOR SECONDARY| ENGLISH MEDIUM
ASSIGNMENT (TMA) - 2024-25
CHEMISTRY
(313)
TUTOR MARKED ASSIGNMENT
Max. Marks: 20
Note: (i) All questions are compulsory. The marks allotted for each question are given at same place.
(ii) Write your name, enrollment number, Al name and subject on the top of the first page of the answer sheet.
हिंदी माध्यम: यहां क्लिक करें
1. Answer any one out of the following questions in about 40 to 60 words. 2
(a) Identify
the group and valency of the element having atomic number 119. Also, predict the
outermost electronic configuration and write the general formula of its oxide. (See
Lesson-3)
Ans:- The
present arrangement of the long form of periodic table can accommodate a
maximum of 118 elements. Thus, according to Aufbau principle, the 8s - orbital
will be filled. In other words, the 119th electron will enter the 8s - orbital.
Thus, its outermost electronic configuration will be 8s1
Since, it has
only one electron in its valence shell, i.e., 8s. Hence its valency will be 1
and it will be in group IA with alkali metals and the formula of its oxide will
be i will M2O where M denotes the element.
(b) Electron
gain enthalpy of chlorine has more negative value as compared to that of fluorine
(F), explain the reason. (See Lesson-3)
Ans:- The
electron gain enthalpy of chlorine is more negative than that of fluorine, and
this is because:
The size of
the atom plays an important role in determining electron gain enthalpy. As we
go down a group in the periodic table, the atomic size increases. Fluorine (F)
is the first element of the halogen group and has a smaller atomic size than
chlorine (Cl), which is the second element of the group.
The reasons
why chlorine has a more negative electron gain enthalpy than fluorine are:-
(i) Atomic
size: The smaller atomic size of fluorine leads to stronger
electron-electron repulsion in the 2p subshell, making it more difficult to
accommodate the extra electron. In contrast, the larger atomic size of chlorine
allows the 3p subshell to better accommodate the incoming electron, resulting
in a more negative electron gain enthalpy.
(ii) Nuclear
charge: As the atomic number increases from fluorine to chlorine, the
nuclear charge also increases. This increased nuclear charge in chlorine
provides a stronger attractive force for the incoming electron, making the
electron gain enthalpy more negative.
(iii)
Shielding effect: In fluorine, the incoming electron has to overcome the
strong shielding effect of the 1s and 2s electrons, whereas in chlorine, the
incoming electron experiences relatively weaker shielding effect from the 1s,
2s and 3s electrons. This makes it easier for the incoming electron to be
accommodated in chlorine, resulting in a more negative electron gain enthalpy.
In short, the
larger atomic size, stronger nuclear charge and weaker shielding effect in
chlorine as compared to fluorine contribute to giving chlorine a more negative
electron gain enthalpy.
2. Answer any one out of the following questions in about
40 to 60 words. 2
(a) How do
metallic and ionic substances differ in conducting electricity? (See Lesson-3)
Ans:- Metals
and ionic substances differ in their ability to conduct electricity as follows:-
Metals conduct
electricity due to the mobility of electrons, while the conductivity of ionic
compounds is due to the mobility of ions.
Specifically:-
(i) Metals:
Metals are good
conductors of electricity because they have a high density of free electrons
that can move freely through the metal lattice.
Metals conduct
electricity in their solid state.
(ii) Ionic
compounds:
Ionic compounds
do not conduct electricity in the solid state because the ions are tightly
bound and cannot move freely.
Ionic compounds
can conduct electricity when molten or dissolved in water, because the ions
become mobile and capable of carrying electric current.
In short,
the main difference is that metals conduct electricity via freely-moving
electrons, whereas ionic compounds require the mobility of their constituent
ions to conduct electricity, which occurs only in the molten or aqueous state.
(b) What is a
unit cell? How many atoms are there in a FCC unit cell? (See Lesson-6)
Ans:- The
unit cell is the smallest repeating unit that defines the structure of a
crystal. It contains all the information needed to construct the entire crystal
by repeating the unit cell in three dimensions.
Face-Centered
Cubic (FCC) Unit Cell:
A face-centered
cubic (FCC) unit cell contains a total of 4 atoms:-
(i) 1 atom at
each of the 8 corners (8 × 1/8 = 1 full atom)
(ii) 1 atom at
the center of each of the 6 faces (6 × 1/2 = 3 full atoms)
Therefore,
the total number of atoms in an FCC unit cell is 4.
3. Answer any one out of the following questions in about
40 to 60 words. 2
(a) The
enthalpy change for the transition of liquid water to steam at temperature 373K
is 40.8 UJ mol-1. Calculate the entropy change for the process. (See
Lesson-10)
Ans:- The
entropy change (ΔS) for the transition from liquid water to steam at 373 K can
be calculated using the following formula:-
ΔS = ΔH / T
Where,
ΔH is the
enthalpy change for the transition (given as 40.8 kJ mol-1)
T is the absolute
temperature (373 K)
Plugging the
values in:-
ΔS = ΔH / T
ΔS = (40.8 kJ
mol-1) / (373 K)
ΔS = 109.38 J
K-1 mol-1
Therefore,
the entropy change for the transition from liquid water to steam at 373 K is
109.38 J K-1 mol-1.
(b) Name two
factors which favor a spontaneous reaction. (See Lesson-10)
Ans:-
According to the findings, the two main factors that determine the spontaneity
of a reaction are:-
(i) Enthalpy
(ΔH)
Enthalpy is the
total heat content of the system.
If a reaction is
exothermic (ΔH is negative), it is spontaneous, as it decreases the energy of
the system.
(ii)
Entropy (ΔS)
Entropy is a
measure of the randomness or disorder in a system.
If a reaction
increases entropy (ΔS is positive), it is spontaneous, as it increases the
disorder of the system.
The Gibbs
free energy change (ΔG) combines these two factors:-
ΔG = ΔH - TΔS
For a reaction
to be spontaneous, ΔG must be negative, which occurs when ΔH is negative
(exothermic) and ΔS is positive (increase in entropy).
To
summarize, the two major factors that promote spontaneous reactions are:-
(i) Negative
enthalpy change (ΔH < 0, exothermic)
(ii) Positive
entropy change (ΔS > 0, increase in disorder)
4. Answer any one out of the following questions in about
100 to 150 words. 4
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