Which Mohr method indicator is used in silver nitrate titration?

Which Mohr method indicator is used in silver nitrate titration?

• A. Potassium chromate
• B. Ferric alum TS
• C. Methyl orange
• D. Phenolphthalein

Answer: (A)

In the Mohr method, you’re titrating chlorides with silver nitrate and need an indicator that signals the endpoint by a visible precipitate forming with the titrant. Potassium chromate fits this role because, after all chloride has been precipitated as silver chloride, any extra silver ions react with chromate to form silver chromate, a distinct brick-red precipitate. That persistent color change clearly marks the endpoint, without relying on pH changes. The other options are not suitable here: they rely on pH indicators or aren’t used to indicate endpoint in this argentometric titration.

In the Mohr method, you’re titrating chlorides with silver nitrate and need an indicator that signals the endpoint by a visible precipitate forming with the titrant. Potassium chromate fits this role because, after all chloride has been precipitated as silver chloride, any extra silver ions react with chromate to form silver chromate, a distinct brick-red precipitate. That persistent color change clearly marks the endpoint, without relying on pH changes. The other options are not suitable here: they rely on pH indicators or aren’t used to indicate endpoint in this argentometric titration.