What is the number of particles or formula units of this chemical eqution?

Question

2NaOH(aq) + CaBr2(aq) ==> Ca(OH)2 + 2NaBr(aq)

Answer 1

This is somewhat ambiguous since we don't know the amount of each reactant, so we cannot determine if all of each reactant is used up and we have only product. In view of that, I'll answer it as it is written assuming we have what is shown in the equilibrium reaction.

NaOH has 2 particles, Na and OH. 2NaOH = 4 particles

CaBr₂ has 3 particles, Ca and 2Br. 1CaBr₂ = 3 particles

Ca(OH)₂ is poorly soluble so will consider it a solid. It has 1 formula unit

NaBr has 2 particles, Na and Br. 2NaBr = 4 particles

Summary:

There are 11 particles and 1 formula unit