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ECE331 Homework #8 Solution
(Due Friday, March 10, 2006)
1. Callister, 9.13
This problem asks us to consider a specimen of ice I which is at -10°C and 1 atm pressure.
(a) In order to determine the pressure at which melting occurs at this temperature, we move
vertically at this temperature until we cross the Ice I-Liquid phase boundar y of Figure 9.33.
This occurs at approximately 570 atm; thus the pressure of the specim en must be raised from
1 to 570 atm.
(b) In order to determine the pressure at which sublimation occurs at this temperature, we
move vertically downward from 1 atm until we cross the Ice I-Vapor phase boundary of Figure
9.33. This intersection occurs at approximately 0.0023 atm.
2. Callister, 9.20
Upon heating a lead-tin alloy of composition 30 wt% Sn-70 wt% Pb from 150°C and utilizing
Figure 9.7:
(a) the first liquid forms at the temperature at which a vertical line at this composition
intersects the eutectic isotherm--i.e., at 183°C;
(b) the composition of this liquid phase corresponds to the intersection with the (α
αα
α + L)-L
phase boundary, of a tie line constructed across the α
αα
α + L phase region just above this
eutectic isotherm--i.e., CL = 61.9 wt% Sn;
(c) complete melting of the alloy occurs at the intersection of this same vertical line at 30 wt%
Sn with the (α
αα
α + L)-L phase boundary--i.e., at about 260°C;
(d) the composition of the last solid remaining prior to complete melting corresponds to the
intersection with α
αα
α-(α
αα
α + L) phase boundary, of the tie line constructed across the α
αα
α + L phase
region at 260°C--i.e., Cα
αα
α is about 13 wt% Sn.
3. Callister, 9.23
The copper-gold phase diagram is constructed below.
