which method do you think is more accurate to determining the concentration of acetic acid in vinegar,the ph meter or the phenopthalein?

pls help me guys!!

pH meter will just tell you the pH of the solution while phenopthlein is an indicator. You can take it from here.

A 'good' pH meter is generally more accurate than determining pH with phenopthalein and your eyeball.

 

That said, accuracy can be 'greatly' improved if you use a good UV/vis to monitor the color change with phenopthalein.

 

So the answer is: it depends on how good your pH meter is vs how you are reading the phenopthalein.

 

With either one, you will greatly increase accuracy by doing a titration.

thanx for your answers

Since phenolphthalein is colourless in netural solutions and colourless in acid solutions I can't see how you could use it (and only it) to measure the strength of an acid like vinegar.

You could use it as the indicator in a titration to get much better accuracy than a pH meter will give you.

Even with the sort of equipment I used at school a titration could tell if the vinegar was 5% or 5.05% With practice and good experimental design you should be able to distinguish 5% from 5.01%

That's a good point and I forgot that it is colorless in neutral to acid solutions.

It is pink to purple basic solutions.....which doesn't do you much good 'except' as JC mentioned above..........

 

Conclusion: You should have more than enough info to answer your homework question.