chemie/ titration?
hier ist eine Frage, die ich nicht wirklich verstehe, warum es so ist… beim c)
Mein Lehrer hat als Indikator Thymolblau benutzt aber ich verstehe nicht warum, denn ich bekam als pH-Wert 3,4 und das ist eine Salpetrige Säure und wenn ich die Tabelle von Indikatoren sehe, macht es für mich gar keinen Sinn warum wir Thymolblau benutzen…
Hier ist die Tabelle, mit dem wir arbeiten:
ich würde zum Beispiel Methylorange benutzen…
kann mir irgendjemand von Chemieexperten helfen?
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Here you have the titration curve, calculated with 12 ml of 1.75 mol/l HNO2 with 1 mol/l NaOH. You can see that the acid is mostly (98.7%) undissociated (red color) at the beginning and is deprotonated in the course of titration to the nitrite (blue). The half equivalence point (pH=pKa=3.4) is 10.5 ml, and the equivalence point (pH=8.65) is 21 ml consumption, with a pH jump of ≅6 to ≅12.
If you carry out the titration with an indicator, it should change in the range from 6 to 12; in your list this applies to bromothymole blue (6.0–7.6), phenolphthalein (8.2–10.0) and thymolphthalein (9.3–10.5). Of these three, phenolphthalein is the best choice because the envelope area is exactly in the middle of the jump area. Thymolblau (8.0–9.6) is also very suitable.
Thank you for your help!!!! I just didn’t understand the pH jump from 6 to 12 so what is that and why do we need that and how is it looked?
Thank you very much!!!
It can be seen from your drawing that the APP is about 9. So you need an indicator to change. Thymolblau does this (but does not stand at all in your table). With phenolphthalein it should also go halfway.
But what do you see?
What?
Yes, of course. I already wrote that in my first answer. But I don’t know phenol purple. Phenolphthalein is the substance.
or?
what do I mean, for example, using phenolphtalin or phenolpurpure?
There’s no Thymolfarblos. You can use any indicator whose envelope point (color change) is in the area of the equivalence point.
So how should I know, for example, that you should use or use thymol blue and why we do not use thymolfarblos or other indicators?