# Help Zone

### Student Question

Secondary IV • 1yr.

hi!

Why can several pH indicators be used in an experiment? How can the appropriate one be determined? Thank you :))

Chemistry

## Explanations (1)

• Explanation from Alloprof

Explanation from Alloprof

This Explanation was submitted by a member of the Alloprof team.

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Team Alloprof • 1yr.

Hello!

All the different acid-base indicators react at different pH, that is, they change color at different locations on the pH scale.

For example, the color-changing point for Bromothymol Blue is between 6.0 and 7.6 on the pH scale, while that of phenolphthalein is between 8.2 and 10.0.

The appropriate indicator can be chosen according to the expected pH of the initial and final solution. It is then possible to see if a change in pH has taken place, by noticing the change in color caused by the indicator.

If the approximate pH of the solution is unknown, one can use several different acid-base indicators with different color-changing points, to estimate the pH of the solution with the color it has in the presence of each of the indicators.