word equation -
3 mol of solid lithium reacts with 1 mol of aqueous gold trichloride to form 3 mol of aqueous lithium chloride and 1 mol of solid gold.
this is a single displacement reaction.
Li is placed above Au in the reactivity series. Therefore Li is more reactive than Au. Since Li is more reactive than Au it can displace Au from the compound AuCl₃.
Therefore its called a single displacement since Li displaces Au from its compound and takes the place of Au and make a new compound AuCl₃.