Question

What type of reagent is required to convert NO2 - to HNO2? [1] base [2] oxidizing agent [3] acid [4] reducing agent [5] precipitating agent

Answer 1

answer: acid

The oxidation state of N is same in both

$NO_2^-$ and $HNO_2$

so there is no oxidation or reduction reaction.

this is a simple acid base reaction :

so it require an Acid.

it reacts in a reversible reaction.

$HNO_2 +H_2O \rightleftharpoons NO_2^- +H^+$

which can be also,

$NO_2^- +H^+\rightleftharpoons HNO_2 +H_2O$