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Analitika NPN i vode

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Question:

Kulometrijsko-amperometrijska titracija - kako se izvodi

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Answer:

1. U rastvoru sa Cl- jonima se uroni Ag elektroda. U otopinu seruma Ag elektroda u određenim vremenskim intervalima opušta jednake količine Ag+ jona. 2. Ag+ i Cl- se spajaju sa jonima iz rastvora (seruma) i nastaje netopivi AgCl 3. Serum je razrijeđen smjesom HNO3/CH3COOH i želatinom grupe koje predstavljaju smetnju su SH iz proteina i halogeni 4. Dok se stvara AgCl ne protiče struja kroz rastvor 5. Kada su svi Cl- joni iz seruma izreagovali tada počinje proticati struja 6. Višak srebra povećava električnu provodljivost otopine, količine Cl- jona se odredi na osnovu vremena u kojem je nastalo dovoljno Ag+ da bi se titritali Cl- joni tj. količina hlorida je propordionalna vremenu WIKI: Reduction of Ag+ back to Ag° generates the current, which signals the endpoint. The titrating reagent contains HNO3, acetic acid, H2O, and either gelatin or polyvinyl alcohol. The HNO3 furnishes nitrate, which is reduced at the generator cathode, forming ammonium ions. The ammonium becomes oxidized back to nitrate at the indicator anode. Gelatin or polyvinyl alcohol is needed to prevent pitting of the generator anode. Acetic acid lowers the solubility of AgCl, preventing dissociation back to Ag+ What Is Anode Pitting? There is a protective film of oxide that reduces the anodic rate of reaction. It is the result of a small area in the metal surface being damaged.


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