complete notes of chemistry.

1. (I fear life more than death because
death is not determined by me but
success or failure; heaven or hell
depends upon my thoughts, walks,
talks and tasks…!)



Chemical Energetics 1 Dr. Sajid Ali Talpur

2. Definitions:
1. Thermodynamics: -the study of conversion and
conservation of heat and other forms of energy
is called thermodynamics.
2. Thermochemistry: - it deals with the
measurement or calculation of heat absorbed or
abandoned in chemical reactions.
3. Thermo chemical reactions: - the chemical
reactions which are accompanied by energy
changes along with the material changes are
generally known as thermochemical reactions.
4. Exothermic reactions: -the chemical reactions
which are accompanied by the liberations or
emission of energy are called exothermic
reactions.
5. Endothermic reactions: -the chemical
reactions which are accompanied by the
absorption of energy are called endothermic
reactions.
6. system: -the collection of matter having certain
boundaries is called system
7. Surroundings:- the environment of a system or
the thing that affect on a system are included in
surroundings.
Chemical Energetics 2 Dr. Sajid Ali Talpur

3. 8. Macroscopic properties: - the properties of a
system in bulk, rather than that of the part the
system which are easily measurable called
macroscopic properties.
9. Intensive properties: -such properties of
system are amount of material independent.
10. Extensive properties: -it is the property that
depends upon the amount of the substance
present in the system.
11. Initial state: -the description of the system
before it suffers any change is called initial state
of the system.
12. Final state: -the description of the system after
it undergoes a change is known as the final state
of the system.
13. State functions: -the physical properties which
depend upon the states of the system (initial and
final) are called state functions.
14. first law of thermodynamics: -according to it:
“The energy in the universe is constant”
OR “the energy can neither be created nor
destroyed, although it may be changed from one
form to another form but the total energy of the
system and the surroundings remains constant.”
Chemical Energetics 3 Dr. Sajid Ali Talpur

4. 15. Hess’s law of constant heat summation: -
“The heat change in a chemical reaction
depends only on the initial and final states of the
system instead of the manner in which it is
brought about”
16. heat of formation: - the change of enthalpy
when one gram mole of a substance is formed
from its elements
17. Standard heat of formation: -the change of
enthalpy when one gram mole of a substance is
formed from its elements at 25oC and 1 atm is
called standard heat of formation.
18. Enthalpy: -the total heat content of a system is
called enthalpy.
19. Entropy: - the disorder of the system is called
entropy.
20. Thermodynamic process: -when a
thermodynamic system changes from one state
to another, the operation is called
thermodynamic process.
Chemical Energetics 4 Dr. Sajid Ali Talpur

5. Scientific Reasons:
Q 1: How can you determine the type of
thermochemical reaction only by touching the
vessel?
Ans. If the vessel wall is cold it means the reaction
inside is endothermic because due to the heat
transfer from surrounding (vessel wall) to the
system has cooled the vessel wall. The reverse is
true for exothermic reaction.
Q 2: Can heat energy be stored in a body?
Ans. No, it is a form of energy in transit which is
transferred from hot to cold body and is converted
into other forms of energy but not stored in the
body.
Q 3: Which of the half filled and full filled glass of
water is denser?
Ans. Both are equally dense because density is an
intensive property which does not depend upon the
amount of material present.
Q 4: Which of the 1 liter and 100 liter water will
boil earlier?
Ans. Once again, boiling point is an intensive
property i.e. independent of the amount of the
material concerned. Hence no matter how much
water is there, it will boil at 100oC at STP.
Chemical Energetics 5 Dr. Sajid Ali Talpur

6. Q 5: Which of the half filled and full filled glass of
water has more internal energy?
Ans. full filled glass, because internal energy is an
extensive property which depends upon the amount
of material concerned.
Q 6: If 100 atom bombs are blasted on earth, will
there be any increase in the energy of the system?
Ans. No, As according to first law of
Thermodynamics;
“Energy is neither created nor destroyed
although it may be converted from one form to
another form”
Consequently, there is no increase in energy, just
the energy stored in the bombs is released but not
created.
Q 7: In which condition all the heat absorbed
becomes the internal energy of the system without
any all.
Ans. During the process at constant volume all the
energy absorbed is equal to the internal energy
because the piston is fixed which neither moves nor
changes volume. Accordingly, there is neither the
work done nor the energy lost.
Chemical Energetics 6 Dr. Sajid Ali Talpur

7. Multiple Choice Questions:
1. ΔH negative represents which reaction?
a) endothermic b) exothermic
c) chemical d) thermochemical
2. Formation of water from hydrogen and oxygen
produces ______ energy.
a) -286 K.J/mole b) +286 K.J/mole
c) -393 K.J/mole d) +393 K.J/mole
3. ∆H positive represents neutralization:
a) true b) false
4. The heat change for the reaction C + O2
→CO2 is called:
a) heat of fusion b) heat of reaction
c) heat of CO2 d) heat of formation
5. In a closed system which remains constant:
a) mass b) energy
c) both d) both are changed
6. heat of a reaction will be more carried in four
steps than a reaction carried in two steps.
a) true b) false
7. All are true according to first law of
thermodynamics except:
a) the energy is increasing due to global
warming
b) energy is constant in the universe.
Chemical Energetics 7 Dr. Sajid Ali Talpur

8. c) sound can be converted to other forms of
energy
d) both a & c e) N.O.T
8. The heat change of a reaction due to the
production of 1 mole of a compound from its
elements is called.
a) heat of reaction b) heat of formation
c) standard heat of form.d) heat of neutralization
9. for the process at constant pressure the work
done will be.
a) maximum b) minimum
c) zero d) negative
10. the standard heat of formation is:
a) positive b) negative
c) zero d) all are possible
11. 1Joule =
a) 4.12c b) 0.24c
c) 41.2c d) 2.4c
12. in a process 200J of heat is absorbed by a
system while 100 joule work is done by the
system. The change in the internal energy is.
a) 50J b) 100J
c) 200J d) 300J
13. in a process 350 J of heat is absorbed by a
system while 50 J work is done on the system.
The change in the internal energy is:
a) 50J b) 100J
Chemical Energetics 8 Dr. Sajid Ali Talpur

9. c) 350J d) 450J
Q 14 – 25
Select from the terms below:
A) Endothermic Reaction B) Exothermic Reaction
14. Combustion reaction is
15. Decomposition reaction is
16. Photosynthesis is
17. Respiration is
18. Bond formation is
19. Bond Breaking is
20. Evaporation is
21. Freezing is
22. Melting is
23. Bomb blast is
24. When products have more energy than the
reactants.
25. If heat content of A is lesser than B then A→B
is.
Chemical Energetics 9 Dr. Sajid Ali Talpur

10. Answer Key.
1 B 2 A 3 B
4 D 5 A 6 B
7 A 8 B 9 A
10 C 11 B 12 B
13 D 14 B 15 A
16 A 17 B 18 B
19 A 20 A 21 B
22 A 23 B 24 A
25 A
Chemical Energetics 10 Dr. Sajid Ali
Talpur