Question

Which indicator would be the best to use for a titration between 0.30 M (CH₃)₂NH with 0.30 M HI? You will probably need to consult the appropriate table in the book.

1. alizarin yellow R, color change at pH 10-12
2. methyl red, color change at pH 4-6
3. bromothymol blue, color change at pH 6-8
4. thymol blue, color change at pH 8-10
5. phenol red, color change at pH 7-9

Answer 1

In this titration you are titrating a weak base (dimethylamine) with strong acid (HI).

For this titration methyl red, color change at pH 4-6 will be the best.

It shows red colour at the endpoing of this titration (which is acidic)

(in basic medium, this indicator shows yellow colour)