acids, pH, and Bases?

Question

common indiactors and thier respective colors
Indiacator Transition pH Acid color Base color

cresol red 0.2-1.8 red yellow
thymol blue 1.2-2.8 red yellow
meythyl orange 3.1-4.4 red yellow
bromocresol green 3.8-5.4 yellow blue
bromocresol purple 5.2-6.8 yellow purple
phenol red 6.4-8.0 yellow red
thymol blue 8.0-9.6 yellow blue
phnolphthalien 8.1-9.6 colorless red
alizarin yellow 10.1-12.0 yellow orange-red

Asoloution involved in a chemical process was to be kept at an acidic pH. Referring back to thetable of indicators, which one(s) would be useful in monitoring this solution and why?

Answer 1

Probably bromocresol purple or phenol red would be the best. Because both those indicators are one color in acidic solutions and a different color in basic solutions.

If you used methyl orange (or any of the other indicators above bromocresol purple), the solution could still be very acidic, but the indicator could be either red or yellow (or which ever colors).

The indicators above phenol red would not be good at all.

Answer 2

I would use a pH meter. It takes the guess work out of using many indicators and is more reliable when properly calibrated.

Answer 3

With all the silly questions I answer, I forget braniacs like you are out there. Kudos.