Question

a chemical species that is present but does not directly participate in a reaction is called a.. select one: there is no such thing catalyst spectator internal standard byproduct

Explanation:

A spectator species (ion or molecule) is present in a reaction mixture but does not take part in the chemical reaction (e.g., spectator ions in ionic reactions that remain unchanged). A catalyst participates (alters reaction rate, is regenerated), an internal standard is for analysis, a byproduct is a reaction product. So the correct term for a species present but not reacting is "Spectator".

Answer:

Spectator (the option labeled "Spectator")