作者polk10203 (123)
看板ChemEng
標題[問題] 材料熱力學求解..
時間Thu Oct 29 16:46:46 2015
題目如下
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?
答案寫說
dδGm x
------- = RT ln[-----] + Ω(1-2x)=0
dx 1-x
在2067 K時 Ωl=38096J → Tcr= Ω/2R = 2291 K
可是在2067K時TiO2應該還在熔點以下
液體混合的δGm不是應該等於
RT(XSiO2*lnXSiO2 + XTiO2*lnXTiO2) +Ω*XSiO2*XTiO2+XTiO2*δG°m,TiO2 嗎
為什麼答案把最後一項δG°m,TiO2 省略掉了
而且在δGm公切點的地方斜率不一定會為0
為什麼答案可以這樣算呢?
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1F：→ polk10203: 我想了想好像是公切線斜率不為0 但 61.227.240.30 10/29 16:55
2F：→ polk10203: 局部低點的切線斜率會是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 感覺像考英文... 182.234.13.82 10/30 12:09