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

Explanation

Electrochemical series : Different metal or metal ion combinations have different values of standard electrode potentials and thus they can be arranged in order of increasing or decreasing values of their standard reduction potentials. The arrangement of various elements in the order of incrcasing values of standard reduction potentials is called electrochemical series. The most reactive elements are kept at the top and the less reactive at the bottom. Standard electrode potential for reduction of hydrogen ion (proton) to hydrogen molecule has been assigned as 0.0 V and it comes in the middle of electrochemical series. Now, if the standard electrode potential of an element is negative (less than zero) then its oxidized form is more stable or hydrogen gas is more stable than the reduced form of that element, hence it can liberate hydrogen gas from acids.