Question

in a aqueous solution of nitrous acid which will be present in high concentration the intact nitrous acid molecule or nitrate ion

Answer 1

Answer 2

In an aqueous solution of nitrous acid (HNO2), the nitrous acid molecules will be present in higher concentration than nitrate ions (NO3-). This is because nitrous acid is a weak acid and does not completely dissociate in water to form nitrate ions. Instead, only a small fraction of the nitrous acid molecules dissociate to form nitrite ions (NO2-) and hydronium ions (H3O+). The equilibrium between nitrous acid and its ions is described by the following equation:

HNO2 + H2O ⇌ NO2- + H3O+

Since nitrous acid is only partially dissociated in water, most of the molecules remain intact in solution and therefore are present in higher concentration than the nitrite and hydronium ions. The exact ratio of intact nitrous acid to nitrite ions depends on the pH of the solution and the acid dissociation constant (Ka) of nitrous acid. At low pH values, the concentration of hydronium ions is high and the equilibrium shifts towards the formation of nitrous acid. At high pH values, the concentration of hydroxide ions is high and the equilibrium shifts towards the formation of nitrite ions.