how do you know when you have spectators ions in equations?

Question

for example if you have
Hydrochloric acid added to sodium carbonate. it becomes
(H+) + (CO3 2-) arrow
CO2 + H2O

Why is sodium and chloride spectator ions?

Answer 1

Because sodium and chloride appear on both sides of the equation and they are unchanged. You start with H+, Cl-, Na+, and CO3 2- on one side and end up with CO2 (which has changed from the CO3), H2O (which has changed from the H and the CO3), Cl- (unchanged), and Na+ (also unchanged)

If that makes sense.