First law of Thermodynamics

Question 1

The 1st law of TD states that

Answer 1

the energy of universe is constant (Law of Conservation of Energy)

Question 2

General energy balance equation

Answer 2

accumulation of energy = (mass flow of energy) + (heat flow of energy) -(energy due to expansion/compression) + (energy due to shaft work) + (energy due to moving fluid)

Question 3

Energy balance for closed systems

Answer 3

dU= Q - PdV
or
dU= Q + W

Question 4

Sign Convention

Answer 4

+Q = endothermic
-Q = exothermic
+W = endergonic
-W = exergonic

Question 5

Internal Energy (U)

Answer 5

total energy of the system in the molecular level

Question 6

Translational Kinetic Energy

Answer 6

Energy associated with the kinetic energy of the molecules as it moves at a certain velocity through space

Question 7

Vibrational Kinetic Energy

Answer 7

Energy associated with the back and forth motion of atoms in a polyatomic molecule about their common center of mass

Question 8

Rotational Kinetic Energy

Answer 8

Energy associated with the rotation of the atoms in a polyatomic molecule about an axis

Question 9

Spin Energy

Answer 9

Energy associated with the rotation of the subatomic particles about their axes

Question 10

Equipartition theorem of energy

Answer 10

states that the total kinetic energy of a system is shared equally among its independent components once the system attains thermal equilibrium.

Question 11

The total energy of a dilute monoatomic gas is

Answer 11

U = U(0) + (3/2)RT

Question 12

The total energy of linear molecules that can roate about two axes

Answer 12

U = U(0) + (5/2)RT

Question 13

The total energy of nonlinear molecules that can rotate about three axes

Answer 13

U = U(0) + 3RT

Question 14

Heat Capacity at Constant Volume

Answer 14

dU = Q_v =(dU/dT)_v = C_vdT
and
C_v = (dU/dT)_v

Question 15

Enthalpy

Answer 15

Measure of the total energy of a thermodynamic system
H = U + PV

Question 16

Hess’ law of heat summation

Answer 16

If a reaction proceeds via several steps, the heat of the overall reaction is the same as the algebraic sum of the heats involved in various steps

Question 17

Standard enthalpy of formation

Answer 17

heat involved in the formation of a compound from its elements in their most thermodynamically stable state

Question 18

Standard enthalpy of combustion

Answer 18

heat released when one mole of a fuel was burned in the presence of oxygen gas to produce carbon dioxide gas and liquid water at 25C and 1 bar

Question 19

Joule-Thompson Effect

Answer 19

describes the temperature change of a fluid when it is forced to flow through a valve or porous plug adiabatically which is known as throttling or isenthalpic process

Question 20

Calorimetry

Answer 20

involves measurement of heat involved in a chemical reaction or physical change

Question 21

Nozzle

Answer 21

device that increases the velocity of the fluid at the expense of pressure

Question 22

diffuser

Answer 22

decreases the velocity resulting in an increase in pressure

Question 23

Compressors, fans, and pumps

Answer 23

devices that increase the pressure of a fluid by the supply of work through a rotating shaft

Question 24

Turbines

Answer 24

devices that generate work fro a flowing fluid

Question 25

Throttling valves

Answer 25

Flow-restricting device