titration q (1 Viewer)

[ND]

Originally posted by +:: $i[Q]u3 ::+
good point.
but then again.. we titrated vinegar wit naoh in class to find the conc. of acetic acid in original indiluted vinegar - a bit dodge when u consider ch3cooh only partially ionises.

But NaOH is a strong base, so when in the solution, the OH- wants H+, which it gets from the CH3COOH, so there's no problem with it.

 

[Constip8edSkunk]

true but consider that in s/s, the pH typically change from like 3-10 in that fraction of titrate added, the use of say phenolphthalein wouldnt affect the results, though the most valid way would b 2 use bromothymol blue probably...

in the titration comp, when we titrated NaOH against HCl, phenolphthalein was used...

 

[ND]

Originally posted by Constip8edSkunk
true but consider that in s/s, the pH typically change from like 3-10 in that fraction of titrate added, the use of say phenolphthalein wouldnt affect the results

I still don't understand.
Wouldn't the pH change from 1-7? (if the acid is in the flask)

 

[Constip8edSkunk]

im talking about how nearing the equivalence pt, the solutions pH changes rapidly, from say like 3 just b4 the equivalence pt to 10 right after that pt, i think there are graphs in most text books representing this.
As its the range where the pH changes so significantly, most indicators can be used to identify the equivalence pt, conversely the w/w titration dun have a significant pH change, using an indicator would b unsuitable.

 

[ND]

Ohh, yeh i understand what you're saying now. Yeh those graphs that look like x=y^3. I don't think the HSC markers would like you using those indicators for it though.\