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Periodicity and Group Chemistry

Halide Ions as Reducing Agents: Iodide, and the Equations

  • 3 things to know
  • Papers 1 and 3

Overview

Why iodide reduces sulfuric acid furthest, the products it gives, and the equations for each reduction.

What you need to know

Answer each one before you reveal it.

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Key term

What happens when solid sodium iodide reacts with concentrated sulfuric acid?

Key term

Why does iodide ion reduce sulfuric acid more extensively than bromide ion?

Key term

What are the possible reduction products of sulfuric acid when it reacts with sodium iodide?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    What happens when solid sodium iodide reacts with concentrated sulfuric acid?

    Model answer

    A vigorous reaction producing purple/violet vapour of iodine, with possible yellow solid (sulfur) and smell of bad eggs (hydrogen sulfide)

  2. 2

    Why does iodide ion reduce sulfuric acid more extensively than bromide ion?

    Model answer

    Iodide ion is a stronger reducing agent than bromide ion because it loses electrons more easily

  3. 3

    What are the possible reduction products of sulfuric acid when it reacts with sodium iodide?

    Model answer

    Sulfur dioxide, sulfur and hydrogen sulfide

  4. 4

    What observation indicates the presence of sulfur dioxide in the reaction of sodium iodide with concentrated sulfuric acid?

    Model answer

    Colourless pungent gas with a choking smell

  5. 5

    What observation indicates the presence of hydrogen sulfide in the reaction of sodium iodide with concentrated sulfuric acid?

    Model answer

    Smell of bad eggs (rotten eggs)

  6. 6

    What observation indicates that iodine has been produced in the reaction of sodium iodide with concentrated sulfuric acid?

    Model answer

    Purple/violet vapour and black/grey solid

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