A t room temperature, disproportionation of an aqueous solution of in situ generated nitrous acid (HNO₂) gives the species

The correct option is H₃O⁺, NO₃⁻ and NO.

Disproportionation is a specific type of redox reaction in which an element in one oxidation state is simultaneously oxidized and reduced to form two different products containing the element in different oxidation states.

In nitrous acid (HNO₂), nitrogen (N) is in the +3 oxidation state.

At room temperature, an aqueous solution of nitrous acid (HNO₂) is unstable and undergoes a disproportionation reaction to form nitric acid (HNO₃, where N is in the +5 oxidation state) and nitric oxide (NO, where N is in the +2 oxidation state). The balanced chemical equation for this disproportionation reaction in aqueous medium is:

$3{\mathrm{HNO}}_2\to {\mathrm{HNO}}_3+2\mathrm{NO}+H_{2}O$

Since the reaction occurs in an aqueous solution, the strong acid nitric acid (HNO₃) dissociates completely in water to yield hydronium ions (H₃O⁺) and nitrate ions (NO₃⁻):

${\mathrm{HNO}}_3+H_{2}O\to H_3{O}^{+}+{\mathrm{NO}}_3^{-}$

Combining these steps, the overall disproportionation reaction of nitrous acid in water can be represented as:

$3{\mathrm{HNO}}_2\to H_3{O}^{+}+{\mathrm{NO}}_3^{-}+2\mathrm{NO}$

Therefore, the species generated during the disproportionation of in situ generated nitrous acid in aqueous solution are H₃O⁺, NO₃⁻, and NO.