How do activity series affect the possibility of a reaction?
If a metal's activity lies beneath the one you are supposed to replace in a single-displacement reaction, the reaction will not proceed.
The activity series or reduction potential helps predict if a reaction will proceed or not. For example in the reaction Cu + HCl. Remember that in the activity series H2>Cu, Hg, Au, Ag. H2 has greater "power" to replace a metal than Cu, hence Cu cannot replace H in HCl and there is no chemical reaction.
"The video shows an experiment to determine the placement of three different metals (Cu, Zn and Mg) on the activity series.
Video from: Noel Pauller"