this is a problem i had:
Half Reaction E°
Mg → Mg2+ + 2e 2.37 V
Mn → Mn2+ + 2e 1.03 V
H2 → 2H+ + 2e 0.00 V
Cu → Cu2+ + 2e 0.16 V
Which of the following reactions is spontaneous?
A. Mn2+ + H2 →
B. Mg + Mn2+ →
C. Mg2+ + Mn →
D. Cu + 2H+ →
E. Mg2+ + Cu →
and the answer is B because:
B
Before checking each choice against the table of oxidation potentials given, it would be
scan the choices and notice that choices B and C are two sides of the same redox reaction:
Mg + Mn2+ → Mg2+ + Mn
Applying a fundamental concept now, that if the forward reaction is not spontaneous,
and vice versa), we can eliminate the other three choices; we need then only determine which
spontaneous as written. According to the tabulated values, the oxidation of magnesium, Mg,
than does manganese, Mn, at 1.03V; larger, more positive values of E0 correspond to more
magnesium is the more likely candidate for oxidation, and choice B is therefore correct.
according to this.. the answer B works because it comes out to be + number... to be spontaneous.. doenst it have to be exo?
