Which of the following ions will always be a spectator ion in a precipitation reaction? (a) Cl–, (b) NO3–, (c) NH4+, (d) S2–, (e) SO42–. Explain briefly.
So in this question we have to determine which is always going a spectator ion. Now here the key to this questions just to say who is always soluble. So whichever compound is always soluble will always be a spectator ion because it will be an ion on both sides of the equation. So basically if we take a look our ions given to us where we have where we have chloride ion , we have nitrate ion, we have ammonium ion, sulphide ion and sulphate ion. So chlorine has exceptions if its connected to let's say silver or led to it becomes a precipitate a solid so it wont be able to be a spectator ion then.
Nitrates are always soluble no matter who there with so this is a choice, ammonium ion is always soluble with whichever its connected to. Sulphides have limitations as well if they're connected to let's say barium they will become a solid so this is out. Same thing with sulphates if it's connected to let's say barium it could be a solid as well its not always soluble. So again key to this question is realizing when they're saying its always going to be a spectator ion they mean that it's always going to be soluble so it will be an ion on both sides of the equation, therefore, it will be a spectator ion