Which type of reaction occurs in the following equation?
2NO2(g) + 2OH"(aq) —— NO2(aq) + NO, (aq) +H2O(1)
a combination redox reaction
a displacement redox reaction
a synthetic redox reaction
a disproportionation redox reaction

A disproportionation redox reaction  

Explanation:

1. Assign an oxidation number to every atom in the equation

2. Identify the atoms that change their oxidation number

N in NO₂: +4 ⟶ +3 in NO₂⁻

N in NO₂: +4 ⟶ +5 in NO₃⁻

3. Identify the type of change

This is a disproportionation — a reaction in which one substance is simultaneously oxidized and reduced.

a 20-cm-long, cylindrical graphite (pure carbon) rod is inserted into an oxidizing atmosphere at 1145 k and 1.013 x 105 pa pressure. the oxidizing process is limited by the diffu- sion of oxygen counterflow to the carbon monoxide that is formed on the cylindrical surface.