Question

When solutions of barium chloride (aq) and sodium sulfate (aq) are mixed, what is/are the spectator ion(s)?

Answer 1

Spectator ions:

• Spectator ions are one which does not participate in the chemical reaction, it remains as same on the reactant and product side
• It remains as a passenger which will not take place in the chemical reaction.
• These ions will be unchanged in the reaction.

Reaction:

• When barium chloride and sodium sulphate react form barium sulphate and sodium chloride are formed.
• It is a double displacement reaction.

$$\begin{gathered} {\mathrm{BaCl}}_2\left(\mathrm{aq}\right)+{\mathrm{Na}}_2{\mathrm{SO}}_4\left(\mathrm{aq}\right)\to {\mathrm{BaSO}}_4\left(\mathrm{s}\right)\downarrow +2\mathrm{NaCl}\left(\mathrm{aq}\right) \\ {\mathrm{Ba}}^{2+}\left(\mathrm{aq}\right)+2{\mathrm{Cl}}^{-}\left(\mathrm{aq}\right)+2{\mathrm{Na}}^{+}\left(\mathrm{aq}\right)+{{\mathrm{SO}}_4}^{2-}\left(\mathrm{aq}\right)\to {\mathrm{BaSO}}_4\left(\mathrm{s}\right)\downarrow +2{\mathrm{Na}}^{+}\left(\mathrm{aq}\right)+2{\mathrm{Cl}}^{-}\left(\mathrm{aq}\right) \end{gathered}$$

• Here, the state of sodium and chloride ions does not change or it remains in the same aqueous state so, sodium and chloride ions are spectator ions.