Arrange the following in order of increasing strength of reducing agents (under standard conditions).?

Arrange the following in order of increasing strength of reducing agents (under standard conditions).





a) Cr ( when losing two e- )





b) H2





c) Zn





d) Li





e) F -





f) Fe ( when losing two e- )








Cr2+ + 2- ↔ Cr Eo = -0.91

Arrange the following in order of increasing strength of reducing agents (under standard conditions).?
If a species ( a metal, a cation or an anion) can easily LOSE electron it is a strong reducing agent. Why?


Since it can easily transfer e- , it removes negative charge and it is oxidized. On the other hand, since it supplies e- to another species, it causes the other substance to be reduced.


How can we compare the e- losing abilities of species to determine their reducing strengths?


We will compare their standard oxidation potentials. The greater the oxidation potential, the stronger the reducing ability or strength.


If we have a table showing only the reduction potentials, how can we compare?


You can do two things.


(1) The greater the reduction potential, the weaker the reducing ability or strength. This means that The smaller the reduction potential, the stronger the reducing ability or strength.


(2) Reverse the reduction equations and change the signs of the potentials, you obtain the oxidation potentials and compare accordingly.





In any case we need the potentials either oxidation or reduction.





The standard reduction potentials of the species involved:





2H+(aq) + 2e− → H2(g) ...................... E° = 0.00 V





Zn2+(aq) + 2e− → Zn(s) ...................... E° = −0.76 V





Li+(aq) + e− → Li(s) ............................. E° = −3.05 V





F2(g) + 2e− → 2F−(aq) ........................ E° = +2.87 V





Fe2+(aq) + 2e− → Fe(s) ....................... E° = −0.44 V





Cr2+(aq) + 2e− → Cr(s) ....................... E° = −0.91 V





The smaller the reduction potential, the stronger the reducing ability or strength.


Li+(aq) + e− → Li(s) ............................. E° = −3.05 V





Li is the strongest reducing agent. Because it is difficult to reduce Li+ ions.


Increasing strenght:


F-


H2


Fe


Zn


Cr


Li