作者theye (Momiji)
看板Chemistry
标题[学习] 一题mass balance
时间Sun Nov 7 13:30:13 2010
最近分析化学学到以系统方法处理化学平衡，
其中，对於写出mass(material) balance则是感到困惑。
‧"the quantity of all species in a solution containing a particular atom
(or group of atoms) must equal the amount of that atom (or group)
delivered to the solution."
‧"it really refers to conservation of atoms, not to mass."
以上两段话皆出自於"Quantitative Chemical Analysis, D. C. Harris, page151"
e.g. CaCl2 in water if species are Ca2+, Cl-, CaCl+, CaOH+
then MB: 2[total calcium] = [total chloride]
=> 2{[Ca2+] + [CaCl-] + [CaOH-]} = {[Cl-] + [CaCl+]}
以上这例子，写出MB不是件难事。
然而，
e.g. ....find the concentrations of the major species in 0.10M NaClO4
saturated with Mn(OH)2. ......
Consider just the following chemistry:
Mn(OH)2 (s) <=> Mn2+ + 2OH- Ksp
Mn2+ + OH- <=> MnOH+ K1
H2O <=> H+ + OH- Kw
写出相关方程式、CB、MB...
卡在MB不晓得是哪两种物种的平衡，於是翻了後面的solution
出现了一个令我不解的等式
[OH-] + [MnOH+] = 2{[Mn2+] + [MnOH-]} + [H+]
species species
containing OH- containing Mn2+
为什麽要加上[H+]呢?
又mass balance的准则到底何在呢?
翻回前段的介绍再读几遍，仍没想通...
所以来请教板上的各位。谢谢噢！
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※ 发信站: 批踢踢实业坊(ptt.cc)
◆ From: 140.118.234.20
1F：推 yutsao:因为OH-的产生除了Mn之外还会有水的解离 11/07 13:41
2F：→ yutsao:其实是[OH-](from Mn) + [MnOH+] = 2{[Mn2+] + [MnOH-]} 11/07 13:42
3F：→ jui8048:承上，加上水的解离就变成[OH-]total+[MnOH]=...+[H+](略) 11/07 14:19
※ 编辑: theye 来自: 140.118.234.20 (11/07 19:28)