Question

What is an electrochemical series? How is it useful in predicting whether a metal can liberate hydrogen from acid or not?

Answer 1

Electrochemical series is a series of chemical elements arranged in order of their standard electrode potentials with respect to hydrogen electrode. Standard hydrogen electrode has reduction potential of zero volt. Therefore, those species with negative standard potential will undergo oxidation and species with positive standard potential will undergo reduction. Also, higher the reduction potential higher is the ability to get reduce or stronger is the oxidising agent.

Metals with negative reduction potential will be strong reducing agent and thus will reduce the $H^{+}$ ion from acid to liberate $H_2$ gas.