Spectator Ion

[Fayola Obasi 1F]

Hey, I was doing question 8 on the second achieve that says NH3 is a weak base so NH4Cl acts as a weak acid. It gives the Kb and the M and asks to calculate the ph of NH4Cl at 25 °C. The hint said that Cl is a spectator ion. What is a spectator ion and how do you identify it?

[Audric Banuelos 1A]

A spectator ion is just an ion that has no participation in the chemical reaction. When you write out the chemical reaction, the ion that is on both the reactants and products side would be the spectator ion. Therefore, you can just cancel each ion on from each side, indicating that it is a spectator ion.

[Yixin Wu 3B]

Hi, I agree that a spectator ion is on both the reactant and product side. I would like to add that you can identify Cl as a spectator ion as it is the conjugate base of a strong acid HCl. A strong acid indicates that all of it is dissociated, so no reverse reaction would happen. As a result, Cl- would not react with water to form HCl, so it is present on both sides of the equation.