The spectator ion in the solution after the precipitation of an insoluble sulfate compound from AgNO3 + K2SO4 is obtained as follows
write the complete equation
that is
2 AgNO3(aq) +K2SO4(aq) = 2KNO3 (aq) + Ag2SO4(s)
the ionic equation
= 2Ag^+(aq) +2NO3^-(aq) 2k^+(aq) + SO4^2- (aq) = 2K^+(aq) + 2NO3^-(aq) + Ag2SO4(s)
the spectator ions is canceled out since they do not take place in reaction
for this case the spectator ion is 2NO3^-(aq) and 2K^+ (aq)
This ions are in aqueous state in both the product side reactant side hence they are spectator ions