Question

Which of the following reactions is most likely to occur? (This question is to test your knowledge of relative reducing powers of metals.)

a. 2Ag + Zn2+ --> 2Ag+ + Zn

b. Au + 3HCl --> AuCl3 + 3/2 H2

c. Cu + 2Li+ --> Cu2+ + 2Li

d. 2K + 2H2O --> 2KOH + H2

I know that the answer is d but could someone explain to me how they got this answer and why the others are not correct. Thank you.

Answer 1

this concept is based on activity series or electrochemical series

in this series elements and ionic species are arranged according to their activity or electrode potential

the element with higher oxidation potential can reduce or replace the element or ion with lower oxidation potential or higher reduction potential

and among the above reaction only this reaction d. 2K + 2H2O --> 2KOH + H2      can take place because in this K has higher oxidation potential   than H2   so is replaced easily