FUPRE PHY221 QUESTIONS 2010/2011
FEDERAL UNIVERSITY OF PETROLEUM RESOURCES EFFURUNCOLLEGE OF SCIENCEDEPARTMENT OF PHYSICSSECOND SEMESTER EXAMINATIONAcademic Session: 2010/2011Course Title: Thermal PhysicsCourse Code: PHY 221 (3 Units)Time Allowed: 2hrs Date: 06/05/2016
Instructions:
Answer all questions in section A and any two (2) questions in section B
SECTION A
1. (a) State Nernst heat theorem.
(b)
A sample of an ideal gas at 1atm pressure expands reversibly and adiabatically
from 1.5dm3 to 4.5 dm3 with an initial temperature of 250C.
calculate:
i.
Its final temperature
ii.
Its final pressure
iii.
The change in entropy
(c)
Explain the following pair of concepts
i.
Relaxation time
ii.
Heat capacities
iii.
Cyclic process
(d)
An initial monoatomic gas at 298k and a pressure of 5atm is expanded to a final
pressure of 1atm under the following conditions
i.
Adiabatically and reversibly
ii.
Adiabatically and
irreversibly
Calculate for each of
the condition
i.
The final temperature of the
gas
ii.
The work done by the gas
iii.
The eat absorbed by the gas
iv.
The change in internal
energy of the gas
v.
The change in the enthalpy
of the gas
(e) calculate
the standard entropy change at 250C for the reaction
H2(g) +
CO2(g) H2O(g) +
CO(g)
Given
the following standard entropies
H2 CO2 H2O CO
S
(J/K/MOL) 130.5 213.8 188.7 197.9
(f) State
the Carnot theorem. A refrigerator in the laboratory rejects heat of about 270C
to its surrounding but operates with its cold reservoir at temperature -50C.
Assuming 200g of H2O melts at 00C, calculate the work done by the
motor of the refrigerator given that the maximum theoretical efficiency of ice (Lf)
is 3.3x105j/kg.
SECTION B
1a. the
Gibb’s free energy of a system is given by the equation
G = H – TS
Where H is the enthalpy, T
the temperature and S the entropy. Use the other thermodynamic potential to
show that
i.
The work done per
temperature increases at constant pressure
ii.
For an irreversible process
at constant temperature and volume, the energy decreases until equilibrium is
achieved.
1b. distinguish clearly
between state and path function
1c. state four
characteristics of entropy
2a. Derive an equation to
show that any change in the entropy of a system is
independent on the
change in pressure of that system.
2b. A monoatomic gas has a
volume of 80cm3 at stp. Assuming the specific heat
capacities at
constant pressure and volume are 1.68 kj/kg/k and 1.20 kj/kg/k
respectively,
calculate
The final temperature
and pressure
i.
The work done on the gas
2c. Write down the general equations for the internal and enthalpy
under the following processes
i.
Adiabatic
ii.
Isochloric
iii.
Ideal gas
3ai. Briefly explain the term
‘equilibrium state’.
3aii. State any three condition
for thermodynamic equilibrium
3b. Show that the fundermental
kinetic equation can be expressed as
Pv
= 1/3Nmu2
State clearly all assumptions
3c. Outline any three significance
of the third law of thermodynamics
4a. Briefly discuss the concept of
‘carnot cycle’ as used in the study of
thermodynamics.
4b. State the zeroth law of
thermodynamics bringing out its implications
4ci. A gas has 1029 atom
at a temperature of 570c. calculate the
i.
Average kinetic energy of
the molecule
ii.
Total energy of the gas(take
k = 1.38 x 10-23j/mol/k)
4cii. Calculate the change in phase from liquid water to vapour at
100oc, the latent heat of vapourization is 22.6x105
j/kg. Assuming the vapour pressure at 100oc is 1atm and Vg and Vf are 1.8m3/kg and 10-3/kg.
calculate the work done in pushing back the atmosphere to make room for the vapour
.
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