18.15 pH Indicators (Video)

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This project was preformed to supply Libretext authors with videos on General Chemistry topics which can be used to enhance their projects. Also, these videos are meant to act as a learning resource for all General Chemistry students.

Video Topics

This video discusses pH indicator and how they are used.

Indicators are usually weak acids

The acid and its conjugate base have different colors

HIn_(aq) + H₂O_(l) ↔ H₃O⁺_(aq) + In^-_(aq)

By le Chatelier's principal

Adding H⁺ shifts the equilibrium to the left. The acid color appears.

Adding ^-OH reduces H₃O⁺ and the equilibrium shifts right. The base color appears.

When {HIn} = {In^-} and intermediate color appears.

This occurs when pH = pKa.

The color change occurs of a range of pH = pKa +/- 1

Acid color pH < pKa -1

Intermediate color pH = pKa

Base color pH > pKa + 1

Link to Video

pH Indicators: https://youtu.be/1IqzUa5lABs

Attribution

Prof. Steven Farmer (Sonoma State University)