Which of the four reactions below will occur (select all that apply)?

Question

Pt_(s) + 2H⁺_(aq) → Pt²⁺_(aq) + H_2(g)

Ni_(s) + 2H⁺_(aq) → Ni²⁺_(aq) + H_2(g)

Sn²⁺_(aq) + H_2(g) → Sn_(s) + 2H⁺_(aq)

2NaF_(aq) + I_2(g) → 2NaI_(aq) + F_2(g)

3Ni²⁺_(aq) + 2Au_(s) → 3Ni_(s) + 2Au³⁺_(aq)

Answer 1

A reaction with negative standard cell potential (E^∘_cell) will not occur.

A reaction with positive standard cell potential (E^∘_cell) will occur.

Pt_(s) + 2H⁺(aq) → Pt²⁺(aq) + H₂(g) E^∘_cell = –1.2 V will not occur

Ni_(s) + 2H⁺(aq) → Ni²⁺(aq) + H₂(g) E^∘_cell = +0.257 V will occur

Sn²⁺(aq) + H₂(g) → Sn(s) + 2H⁺(aq) E^∘_cell = –0.1262 V will not occur

2NaF(aq) + I₂(g) → 2NaI(aq) + F₂(g) E^∘_cell = –2.3305 V will not occur

3Ni²⁺(aq) + 2Au(s) → 3Ni(s) + 2Au³⁺(aq) E^∘_cell = –1.755 V will not occur

The E^∘_cell values were calculated from Standard Reduction Potentials at 25 °C which are found tabulated in various sources (and can looked up online).

Answer

Of the five reactions, only

Ni_(s) + 2H⁺(aq) → Ni²⁺(aq) + H₂(g)

will occur spontaneously.