P3C.9 At low temperatures there are two contributions to the heat capacity of a metal, one associated with lattice vibrations, which is well-approximated by the Debye T-law, and one due to the valence electrons. The latter is linear in the temperature. Overall, the heat capacity can be written (a) Assuming that the expression given above for the heat capacity applies, explain why a plot of C,m(T)/T against T² is expected to be a straight line with slope a and intercept b. (b) Use such a plot to determine the values of the constants a and b. (c) Derive an expression for the molar entropy at temperature T. (Hint: you will need to integrate Cm(T)/T.) (d) Hence determine the molar entropy of potassium at 2.0 K. Debye electronic Cp.m (T)= aT³ + bT The molar heat capacity of potassium metal has been measured at very low temperatures to give the following data T/K 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 0.437 0.560 0.693 0.838 0.996 1.170 1.361 1.572 (JK' mol')
P3C.9 At low temperatures there are two contributions to the heat capacity of a metal, one associated with lattice vibrations, which is well-approximated by the Debye T-law, and one due to the valence electrons. The latter is linear in the temperature. Overall, the heat capacity can be written (a) Assuming that the expression given above for the heat capacity applies, explain why a plot of C,m(T)/T against T² is expected to be a straight line with slope a and intercept b. (b) Use such a plot to determine the values of the constants a and b. (c) Derive an expression for the molar entropy at temperature T. (Hint: you will need to integrate Cm(T)/T.) (d) Hence determine the molar entropy of potassium at 2.0 K. Debye electronic Cp.m (T)= aT³ + bT The molar heat capacity of potassium metal has been measured at very low temperatures to give the following data T/K 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 0.437 0.560 0.693 0.838 0.996 1.170 1.361 1.572 (JK' mol')
Chemistry
10th Edition
ISBN:9781305957404
Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Publisher:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Chapter1: Chemical Foundations
Section: Chapter Questions
Problem 1RQ: Define and explain the differences between the following terms. a. law and theory b. theory and...
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Transcribed Image Text:P3C.9 At low temperatures there are two contributions to the heat capacity of
a metal, one associated with lattice vibrations, which is well-approximated by

Transcribed Image Text:the Debye T-law, and one due to the valence electrons. The latter is linear in
the temperature. Overall, the heat capacity can be written
(a) Assuming that the expression given above for the heat capacity applies,
explain why a plot of C,m(T)/T against T² is expected to be a straight line
with slope a and intercept b. (b) Use such a plot to determine the values
of the constants a and b. (c) Derive an expression for the molar entropy
at temperature T. (Hint: you will need to integrate Cm(T)/T.) (d) Hence
determine the molar entropy of potassium at 2.0 K.
Debye electronic
Cp.m (T)= aT³ + bT
The molar heat capacity of potassium metal has been measured at very low
temperatures to give the following data
T/K
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.55
0.437 0.560 0.693 0.838 0.996 1.170 1.361 1.572
(JK' mol')
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