Thermodynamics

Question 1

Statement 1: The laws of thermodynamics deal with energy changes of microscopic systems rather than macroscopic systems containing a large number of molecules.
Statement 2: Laws of thermodynamics apply only when a system is in equilibrium or moves from one equilibrium state to another equilibrium

Answer 1

Statement 1 is incorrect and 2 is correct
The laws of thermodynamics deal with energy changes of macroscopic systems involving a large number of molecules rather than microscopic
systems containing a few molecules.

Question 2

Statement 1:A system in thermodynamics refers to that
part of universe in which observations are
made and remaining universe constitutes
the surroundings.
Statement 2: system as separated from the
surroundings by some sort of wall which may
be real or imaginary called as boundary

Answer 2

Both statements are correct

Question 3

Internal energy, U of the system may change, when
3 conditions

Answer 3

• heat passes into or out of the system,
• work is done on or by the system,
• matter enters or leaves the system.

Question 4

Statement 1: W(adiab) is positive when work is done on the
system and the internal energy of system
increases.
Statement 2: if the work is done by the
system, W(adiabatic)will be negative because internal
energy of the system decreases.

Answer 4

Both statements are correct

Question 5

Statement 1 q is positive, when heat
is transferred from the surroundings to the
system and the internal energy of the system
increases
Statement 2: q is negative when heat is
transferred from system to the surroundings
resulting in decrease of the internal energy of
the system.

Answer 5

Both statements are correct

Question 6

∆U = q + w is
mathematical statement of the first law of
thermodynamics, which states that
The energy of an isolated system is……………
.

Answer 6

constant

Question 7

Process or change is said to be
reversible, if 3 conditions

Answer 7

process could, at any moment,be reversed by an infinitesimal change.
process proceeds infinitely slowly by a series of equilibrium states
system and the surroundings are
always in near equilibrium with each other.

Question 8

Statement 1:An extensive property is a
property whose value is independent of the quantity
or size of matter present in the system.
Statement 2: Properties which depend
on the quantity or size of matter present
are known as intensive properties.

Answer 8

Both statements are incorrect
Extensive: depend on quantity……..
Intensive: are independent of quantity……..

Question 9

Assertion: For Water a lot of energy is needed to raise its temperature.
Reason: Water has a large heat capacity, When C is large, a given amount of heat results in only a small temperature rise.

Answer 9

Both assertion and reason are correct and reason correctly explain assertion

Question 10

We define …………. As heat required to raise the temperature of one unit mass of a substance by one degree celsius (or one kelvin)

Answer 10

Specific heat capacity

Question 11

We can measure energy changes associated
with chemical or physical processes by an
experimental technique called………..

Answer 11

calorimetry

Question 12

Heat absorbed at constant………..is measured in a bomb
calorimeter

Answer 12

volume

Question 13

Since the bomb calorimeter is sealed, its volume does not change so no………. Is done as the reaction is carried out at constant…………

Answer 13

Work
Volume

Question 14

The standard enthalpy of reaction is the
enthalpy change for a reaction when all
the participating substances are in their………….

Answer 14

standard states.

Question 15

The standard state of a substance at a
specified temperature is its pure form at pressure………

Answer 15

1 bar

Question 16

The enthalpy change that accompanies
melting of one mole of a solid substance in
standard state is called…………….

Answer 16

standard enthalpy
of fusion or molar enthalpy of fusion,
∆fusH

Question 17

Amount of heat required to vaporize one
mole of a liquid at constant temperature
and under standard pressure (1bar) is called
its…………

Answer 17

standard enthalpy of vaporization or
molar enthalpy of vaporization,
.

Question 18

………………is the change in enthalpy when one mole of a solid substance sublimes at a constant temperature and under standard pressure (1bar).

Answer 18

Standard enthalpy of sublimation, subH

Question 19

Assertion: Thus, it requires less heat to vaporise 1 mol of acetone than it does to vaporize 1 mol of water.
Reason: The magnitude of the enthalpy change depends on the strength of the intermolecular interactions in the substance undergoing the phase transfomations.

Answer 19

Both are correct and R is correct explanation of A

the strong hydrogen bonds between water molecules hold them tightly in liquid phase.
For an organic liquid, such as acetone, the intermolecular dipole-dipole interactions are significantly weaker.

Question 20

The standard enthalpy change for the formation of one mole of a compound from its elements in their most stable states of aggregations is called………….

Answer 20

standard molar enthalpy of Formation.

Question 21

By convention, standard enthalpy for formation, of an element in reference state, i.e., its most stable state of aggregation is taken as.

Answer 21

zero

Question 22

A balanced chemical equation together with the value of its ∆r H is called a…………

Answer 22

thermochemical equation

Question 23

If a reaction takes place in several steps then its standard reaction enthalpy is the sum of the standard enthalpies of the intermediate reactions into which the overall reaction may be divided at the same temperature.
True or false

Answer 23

True

Question 24

………………… is defined as the enthalpy change per mole (or per unit amount) of a substance, when it undergoes combustion and all the reactants and products being in their standard states at the specified temperature.

Answer 24

Standard enthalpy of combustion

Question 25

Cooking gas in cylinders contain mostly……….

Answer 25

Butane

Question 26

Combustion of glucose gives out………..of heat

Answer 26

2802kJ/mole

Question 27

It is the enthalpy change on breaking one mole of bonds completely to obtain atoms in the gas phase.

Answer 27

Enthalpy of atomisation

Question 28

The……………..is the change in enthalpy when one mole of covalent bonds of a gaseous covalent compound is broken to form products in the gas phase.

Answer 28

bond dissociation enthalpy

Question 29

The…………..of an ionic compound is the enthalpy change which occurs when one mole of an ionic compound dissociates into its ions in gaseous state

Answer 29

lattice enthalpy

Question 30

Ionization energy and electron affinity are defined at absolute zero. At any other temperature, heat capacities for the reactants and the products have to be taken into account
True or false

Answer 30

True

Question 31

……………..of a substance is the enthalpy change when one mole of it dissolves in a specified amount of solvent

Answer 31

Enthalpy of solution

Question 32

………….. at………….dilution is the enthalpy change observed on dissolving the substance in an infinite amount of solvent when the interactions between the ions (or solute molecules) are negligible.

Answer 32

The enthalpy of solution

infinite

Question 33

For most of the ionic compounds, ∆solH is………and the dissociation process is………..

Answer 33

positive

endothermic

Question 34

Assertion: Many fluorides tend to be less soluble than the corresponding chlorides
Reason: If the lattice enthalpy is very high, the dissolution of the compound may not take place at all.

Answer 34

Both are correct and R is correct explanation of A

Question 35

As more and more solvent is used, the enthalpy of solution approaches a limiting value, i.e, the value in infinitely dilute solution.
True or false

Answer 35

True

Question 36

…………… means ‘having the potential to proceed without the assistance of external agency’. However, it does not tell about the………….

Answer 36

spontaneity

rate of the reaction or process.

Question 37

A…………..process is an irreversible process and may only be reversed by some external agency.

Answer 37

spontaneous

Question 38

In an isolated system, there is always a tendency for the systems’ energy to become more…………..

Answer 38

disordered or chaotic

Question 39

Statement 1:Temperature is the measure of average chaotic motion of particles in the system.
Statement 2: Heat added to a system at lower temperature causes lesser randomness than when the same quantity of heat is added to it at higher temperature.

Answer 39

Statement 1 is correct but statement 2 is incorrect

Heat added to a system at lower temperature causes greater randomness than when the same quantity of heat is added to it at higher temperature.

Question 40

Statement 1: If the system is in thermal equilibrium with the surrounding, then the temperature of the surrounding is same as that of the system.
Statement 2: But increase in enthalpy of the surrounding is not equal to decrease in the enthalpy of the system.

Answer 40

Statement 1 is correct but 2 is incorrect

increase in enthalpy of the surrounding is equal to decrease in the enthalpy of the system.

Question 41

Assertion: Exothermic reactions are spontaneous in nature
Reason: In exothermic reactions heat released by the reaction increases the disorder of the surroundings and overall entropy change is positive which makes the reaction spontaneous.

Answer 41

Booth are correct and R is correct explanation of A

Question 42

Assertion: The entropy of any pure crystalline substance approaches zero as the temperature approaches absolute zero. This is called third law of thermodynamics.
Reason: This is so because there is perfect order in a crystal at absolute zero.

Answer 42

Both are correct and R is correctly explanation of A

Question 43

Assertion: Statement of third law of thermodynamics is confined to pure crystalline solids only
Reason: theoretical arguments and practical evidences have shown that entropy of solutions and super cooled liquids is not zero at 0 K.

Answer 43

Both are correct and R is correct explanation of A

Question 44

In case of compression the work done in………… process is less than done in…………..

Answer 44

Reversible
Irreversible
Irreversible > reversible
Opposite for expansion

Question 45

Assertion:In case of expansion maximum amount of work is obtained by reversible process
Reason: Less heat is lost to the surrounding

Answer 45

Both are correct and R is correct explanation of A

Question 46

If question says isoenthalpic process then work………

Answer 46

Work is Pext*V

Question 47

The free energy change (AG°) is negative when -
1. The surroundings do no electrical work on the system.
2. The surroundings do electrical work on the system.
3. The system does electrical work on the surroundings.
4. The system does no electrical work on the surroundings.

Answer 47

3 is correct