Question

which is a spectator ion in the reaction between NaOH(aq) and H2SO4(aq)?

Answer 1

The reaction between NaOH and H2SO4 is a reaction between an acid and a base which means the reaction is a neutralization that produces products of salt and water. The salt is Na2SO4. 
spectator ions are ions that are found at the both sides of the equation when the aqueous components are in their ionic forms. In this case, when breaking down of components is applied, the spectator ions are Na + and SO4 2- . 

Answer 2

Answer : The spectator ions are, $OH^-$  and $H^+$

Explanation :

Spectator ions : It is defined as the ions present on reactant and product side which do not participate in a reactions. That means the same ions present on both the sides.

In the net ionic equations, we are not include the spectator ions in the equations.

The given balanced ionic equation will be,

$2NaOH(aq)+H_2SO_4(aq)\rightarrow 2H_2O(aq)+Na_2SO_4(s)$

The ionic equation in separated aqueous solution will be,

$2Na^+(aq)+2OH^-(aq)+2H^+(aq)+SO_4^{2-}(aq)\rightarrow Na_2SO_4(s)+2H^+(aq)+2OH^-(aq)$

In this equation, $OH^-\text{ and }H^+$ are the spectator ions.

By removing the spectator ions from the balanced ionic equation, we get the net ionic equation.

The net ionic equation will be,

$2Na^+(aq)+SO_4^{2-}(aq)\rightarrow Na_2SO_4(s)$

Therefore, the spectator ions are, $OH^-$  and $H^+$