Nitrite Confirmatory Test Simulator

Starch-Iodide Test

Confirmatory Test for Nitrite (NO₂⁻) Ions in Qualitative Analysis.

1. Setup Experiment

Select Unknown Salt Mixture

Sodium Nitrite (NO₂⁻) + KI + Starch Sodium Nitrate (NO₃⁻) + KI + Starch [Control]

2. Observation

Solution Color Slightly Cloudy

Status: Standby.
Select an aqueous salt mixture containing Potassium Iodide (KI) and Starch indicator. Addition of Dilute Acetic Acid (CH₃COOH) will trigger the redox reaction.

3. Chemical Principles

Redox Chemistry: In a mildly acidic medium, Nitrite (NO₂⁻) acts as a strong enough oxidizing agent to convert Iodide (I⁻) into free Iodine (I₂).

2NO₂⁻ + 2I⁻ + 4H⁺ → 2NO↑ + I₂ + 2H₂O

Complexation: The free Iodine (I₂) immediately slips into the helical structure of the amylose polymer (Starch) to form an intensely colored Blue-Black inclusion complex.

Visual Key

Salt + KI + Starch (Cloudy)

Dilute Acetic Acid

Starch-Iodine Complex (Blue-Black)

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