作者jg065 (相信"相信的力量")
看板Chemistry
標題Re: [問題] buffer solution配置
時間Mon Jan 21 02:39:58 2013
先用等濃度的磷酸和氫氧化鈉做滴定到pH=6.2
並記錄兩者的體積比(Va:Vb)
因為濃度相同，所以"體積比=莫耳數比"
又題目要起始磷酸是1.0M且總體積為1L
所以磷酸要1.0M * 1.0L = 1.0mole
接下來算氫氧化鈉所需的莫耳數，設nb
所以1.0 : nb = Va : Vb
算好後就取磷酸98.0克，氫氧化鈉取(40.0*nb)克
用容量瓶配成一升就好了
※ 引述《newman000 (紐曼)》之銘言：
: 最近有作到一題
: 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.)
: 是有想說配1M的[H3PO4]然後用NaOH滴定到pH6.2時
: 可是不知道要用多少濃度的NaOH，以即怕1M的濃度因為加入NaOH後因體積改變而跑掉
: 想問板上有沒有甚麼方法可以去配置
: 文有點長
: 謝謝!!!
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