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发表于 23-2-2008 11:09 AM
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楼主 |
发表于 23-2-2008 06:45 PM
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发表于 23-2-2008 07:33 PM
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发表于 23-2-2008 09:35 PM
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发表于 23-2-2008 09:49 PM
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原帖由 LOO5O 于 23-2-2008 09:35 PM 发表 
我用的是文言文，以前人都是想不到字时就用另一个同音的字代替它。你们读中国文学的应该知道吧？
还敢绞辩。。。。。。。。:@ |
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发表于 23-2-2008 09:55 PM
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原帖由 khookw64 于 23-2-2008 21:49 发表
还敢绞辩。。。。。。。。:@
没有狡辩，不相信可以去查你的书！ |
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发表于 24-2-2008 07:39 AM
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发表于 24-2-2008 07:41 AM
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发表于 24-2-2008 07:43 AM
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发表于 24-2-2008 07:44 AM
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无聊完了...
继续K书... |
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发表于 24-2-2008 09:32 AM
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发表于 26-2-2008 06:48 PM
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楼主 |
发表于 26-2-2008 10:02 PM
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什么是buffer solution?????????? |
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发表于 27-2-2008 05:07 PM
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回复 293# nejiru 的帖子
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去STPM专区求助啦！ |
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发表于 27-2-2008 05:09 PM
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回复 293# nejiru 的帖子
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去STPM专区求助啦！ |
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发表于 27-2-2008 08:34 PM
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大家好～
我又回来走走，顺便拿分 |
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发表于 27-2-2008 09:16 PM
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原帖由 nejiru 于 26-2-2008 10:02 PM 发表 
什么是buffer solution??????????
应该是chemistry的吧。
HA(aq) + H2O(l) → H3O+(aq) + A−(aq) ，恩给你一个formula了。
给你notes :
Buffer solutions are solutions that resist change in Hydronium ion and the hydroxide ion concentration (and consequently pH) upon addition of small amounts of acid or base, or upon dilution. Buffer solutions consist of a weak acid and its conjugate base (more common) or a weak base and its conjugate acid (less common). The resistive action is the result of the equilibrium between the weak acid (HA) and its conjugate base (A− :
HA(aq) + H2O(l) → H3O+(aq) + A−(aq) Any alkali added to the solution is consumed by the Hydronium ions. These ions are mostly regenerated as the equilibrium moves to the right and some of the acid dissociates into Hydronium ions and the conjugate base. If a strong acid is added, the conjugate base is protonated, and the pH is almost entirely restored. This is an example of Le Chatelier's principle and the common ion effect. This contrasts with solutions of strong acids or strong bases, where any additional strong acid or base can greatly change the pH. This may be easier to see by comparing two graphs when an strong acid is titrated with a strong base the curve will have a large gradient throughout showing that a small addition of base/acid will have a large effect compared to a weak acid/strong base titration curve which will have a smaller gradient near the pKa.
When writing about buffer systems they can be represented as salt of conjugate base/acid, or base/salt of conjugate acid. It should be noted that here buffer solutions are presented in terms of the Brønsted-Lowry notion of acids and bases, as opposed to the Lewis acid-base theory (see acid-base reaction theories). Omitted here are buffer solutions prepared with solvents other than water.
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发表于 27-2-2008 09:18 PM
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Calculating pH
The equilibrium above has the following acid dissociation constant:
Simple manipulation with logarithms gives the Henderson-Hasselbalch equation, which describe pH in terms of pKa:
In this equation
[A−] is the concentration of the conjugate base. This may be considered as coming completely from the salt, since the acid supplies relatively few anions compared to the salt lyn.
[HA] is the concentration of the acid. This may be considered as coming completely from the acid, since the salt supplies relatively few complete acid molecules (A − may extract H + from water to become HA) compared to the added acid.
Maximum buffering capacity is found when pH = pKa, and buffer range is considered to be at a pH = pKa ± 1. |
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