作者jg065 (相信"相信的力量")
看板Chemistry
标题Re: [问题] buffer solution配置
时间Mon Jan 21 02:39:58 2013
先用等浓度的磷酸和氢氧化钠做滴定到pH=6.2
并记录两者的体积比(Va:Vb)
因为浓度相同，所以"体积比=莫耳数比"
又题目要起始磷酸是1.0M且总体积为1L
所以磷酸要1.0M * 1.0L = 1.0mole
接下来算氢氧化钠所需的莫耳数，设nb
所以1.0 : nb = Va : Vb
算好後就取磷酸98.0克，氢氧化钠取(40.0*nb)克
用容量瓶配成一升就好了
※ 引述《newman000 (纽曼)》之铭言：
: 最近有作到一题
: Suppose that you are a teaching assistant ic a university and you have to
: provide your students the procedures of preparing a buffer solution,plaease
: do your best to write down a step-by-step instruction for your students.The
: buffer solution should have the following requirement:1.0L,pH6.2,and1.0M
: phosphate (i.e.,[H3PO4]+[H2PO4 -]+[HPO4 2-]+[PO4 3-]=1.OM).Assuming that your
: theaching lab had balances,pH meters and electrodes,beakers,volumetirc flask,
: magnetic stirrers,deionized water,and necessary chemicals including HCl
: (fw 36.5),NaOH (fw 40.0),H3PO4 (fw 98.0),KH2PO4(fw 136.1),K2HPO4(fw174.2),ete.
: (Note:to answer this question,it is not encouraged to do any calculation
: involving pKa.)
: 是有想说配1M的[H3PO4]然後用NaOH滴定到pH6.2时
: 可是不知道要用多少浓度的NaOH，以即怕1M的浓度因为加入NaOH後因体积改变而跑掉
: 想问板上有没有甚麽方法可以去配置
: 文有点长
: 谢谢!!!
--
※ 发信站: 批踢踢实业坊(ptt.cc)
◆ From: 1.160.237.235