Question

1) determine which of the following pairs of reactants wil result in a spontaneous reaction at 25C

A) Sn4+ (Aq) + Mg(s)

B) Cr3+ (aq) + Ni(s)

C) Zn(s) + Na+ (aq)

D) Cd(s) + Ba2+ (aq)

e) none of the above

Answer 1

We need to compare reduction potentials

Sn4+ + 2 e− ⇌ Sn2+ +0.15

Mg2+ + 2 e− ⇌ Mg(s) −2.372

Clearly, Sn4+ has a higher potential to reduce, so this is likely to happen

Sn4+ + Mg(s) = Sn2+ + Mg+2

B)

Cr3+ + 3 e− ⇌ Cr(s) −0.74

Ni2+ + 2 e− ⇌ Ni(s) −0.25

Nickel is likely to remain as Ni(s) since it has higher potential, so this is no reaction

C)

Na+ is very reactive, it is not likely to form Na(s) over Zinc

D)

Ba2+ is much more reactive than Cd(s)

E)

form the list: A happens spontaneously

Choose A)

A) Sn4+ (Aq) + Mg(s)