Question

net ionic equation for HNO2 and NaOH in H2O

Answer 1

HNO2(aq) + NaOH(aq) --> NO2-(aq) + H2O(l) + Na+(aq)
this is the ionic equation
HNO2(aq) + Na+(aq) + OH-(aq) --> NO2-(aq) + H2O(l) + Na+(aq)
this is the net ionic equation
HNO2(aq) + OH-(aq) --> NO2-(aq) + H2O(l)

Answer 2

nitrous acid is a weak acid what this means is that it will not dissociate to a large degree in aqueous solution. Sodium hydroxide is a strong base andwill dissociate completely. There are a couple of ways to write the equation:
this is the molecular equation
HNO2(aq) + NaOH(aq) --> NO2-(aq) + H2O(l) + Na+(aq)
this is the ionic equation
HNO2(aq) + Na+(aq) + OH-(aq) --> NO2-(aq) + H2O(l) + Na+(aq)
this is the net ionic equation
HNO2(aq) + OH-(aq) --> NO2-(aq) + H2O(l)

Generally with acid base we leap directly to the net ionic equation.
sodium is the only spectator ion because the OH- become water and nitrus acid is a weak acid.