What is an effective way to slow down or stop this reaction in aqueous solution?

NaOH (aq) + KCI (aq) - > NaCI (aq) + KOH (aq)

increase the pressure of the reaction mixture

increase the surface area of the reactants

add a catalyst to the reaction mixture

add a lot of water to the reaction mixture

Add a lot of water to the reaction mixture.

Explanation:

The rate of the reaction is directly proportional to the concentration of the reactants.

So, adding a lot of water to the reaction mixture will decrease the concentration of the reactants. Thus, it slows down or stop the reaction.

Pressure has no effect on the reaction since the reactants and products are in aqueous phase.

Increasing the surface area of the reactants will increase the rate of the reaction.

Add a catalyst to the reaction mixture will increase the rate of the reaction since it lowers the activation energy required to initiate the reaction.

So, the right choice is:

add a catalyst to the reaction mixture