作者polk10203 (123)
看板ChemEng
标题[问题] 材料热力学求解..
时间Thu Oct 29 16:46:46 2015
题目如下
SiO2,which melts at 1723°C,and TiO2, which melts at 1842°C, are immiscible
in the solid state, and the SiO2-TiO2 binary system contains a monotectic
equilibrium at 1794°C, at which temperature virtually pure TiO2 is in
equilibrium with two liquids containing mole fractions of SiO2 of 0.04 and
0.76. If, for the purpose of simple calculation, it is assumed that the
compositions of the two liquids are XSio2=0.24 and XSiO2=0.76 and that the
liquid solutions are regular in their behavior, what is the value of Ωl
and at what temperature does the liquid immiscibility gap disappear?
答案写说
dδGm x
------- = RT ln[-----] + Ω(1-2x)=0
dx 1-x
在2067 K时 Ωl=38096J → Tcr= Ω/2R = 2291 K
可是在2067K时TiO2应该还在熔点以下
液体混合的δGm不是应该等於
RT(XSiO2*lnXSiO2 + XTiO2*lnXTiO2) +Ω*XSiO2*XTiO2+XTiO2*δG°m,TiO2 吗
为什麽答案把最後一项δG°m,TiO2 省略掉了
而且在δGm公切点的地方斜率不一定会为0
为什麽答案可以这样算呢?
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1F：→ polk10203: 我想了想好像是公切线斜率不为0 但 61.227.240.30 10/29 16:55
2F：→ polk10203: 局部低点的切线斜率会是0 61.227.240.30 10/29 16:57
3F：推 archie4ni: 你想看看immiscibility gap disappear 182.234.13.82 10/30 12:08
4F：→ archie4ni: 的意思 感觉像考英文... 182.234.13.82 10/30 12:09