Chapter 7 Vacancies
1.
Gold has a melting point of 1,063C and its latent heat of fusion is 12,700 J/mol.
Determine the entropy change due to the freezing of one mole of gold, and
indicate whether it is positive or negative.
2.
When a mole of gold freezes at its freezing point, is there a change in its internal
energy? Explain.
5.
Consider an insulated chamber with two equally sized compartments that are
separated from each other by a removable partition. Initially one of the
compartments is assumed to be evacuated completely while the other is filled
with a mole of an ideal gas under standard atmospheric conditions. Now consider
that the partition is removed so that the gas can expand to fill the two chambers.
(a) Will there be a change in the temperature of the gas? Explain. (b) Compute
the value of the entropy change.
6.
Consider that the two compartments of the insulated box of Prob. 7.5 initially
contain on one side a mole of ideal gas A and on the other side a mole of ideal
gas B, with both gases at a pressure of 0.1013 MPa and a temperature of 298 K.
Now assume that the partition is removed.
(a) How large will the enthalpy change be? (b) Compute the entropy change. (c)
Compute the Gibbs free-energy change. Is the magnitude of this change
significant? Explain.
8. Compute the equilibrium concentration of vacancies in pure copper at 700C. (Hf:
83,700 J/mol, R: 8.314 J/molK)
11. (a) It has been estimated that the enthalpy for the formation of self-interstitial
atoms in copper is about 385,000 J/mol. Compute the equilibrium concentration
of these interstitial atoms in copper at 1000K. (b) The activation energy for the
movement of the self-interstitials atoms in copper is believed to be about 9,640
J/mol. Estimate the jump frequency of the interstitials at 1000K. (vibration
frequency: 1015 s-1)