Interaction | Reaction | Process     Data Page

In the lab, the addition of conc. sulfuric acid to sodium iodide gives HI gas. HOWEVER, the hydrogen iodide formed is further oxidised by sulfuric acid to iodine and the sulfuric acid is reduced to SO2. The HI reacts with SO2 to give I2 and sulfur. Finally, the HI reacts with sulfur to give I2 and hydrogen sulfide.

Thus, the action of conc. sulfuric acid on solid sodium iodide gives a complex mixture of: HI, SO2, S, H2S and I2.

Observations: yellow sulfur, smell of bad eggs (H2S), purple fumes or black solid of iodine.

2
NaI
  +  
H2SO4
         
2
HI
  +  
Na2SO4
Reactant Page Go To Go To
Sodium iodide     Reactions Using    Reactions Forming
Sulfuric acid     Reactions Using    Reactions Forming
Hydrogen iodide     Reactions Using    Reactions Forming
Sodium sulfate     Reactions Using    Reactions Forming

Interaction, Reaction, Process defined as:
British A-Level Chemistry: A2
British A-Level Chemistry: AS
Oxidation: Of Substrate By Reagent
Proton transfer: Brønsted reaction
Redox
Sodium Halides + conc. H2SO4

© Mark R. Leach 1999 –


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