Question

Predict whether the following reactions would occur spontaneously in aqueous solution at 25 °C. Assume that the initial concentrations of dissolved species are all 1.0 M

Predict whether the following reactions would occur spontaneously in aqueous solution at 25 °C. Assume that the initial concentrations of dissolved species are all 1.0 M

Predict whether the following reactions would occur spontaneously in aqueous solution at 25 °C. Assume that the initial concentrations of dissolved species are all 1.0 M

Predict whether the following reactions would occur spontaneously in aqueous solution at 25 °C. Assume that the initial concentrations of dissolved species are all 1.0 M

Ca (s) + Cd ²⁺ (aq) ----> Ca²⁺ (aq) + Cd (s)

2Br ^- (aq) + Sn²⁺ (aq) ----> Br₂ (l) + Sn (s)

2Ag (s) + Ni²⁺ (aq) ----> 2Ag⁺ (aq) + Ni (s)

Cu⁺ (aq) + Fe³⁺ (aq) ----> Cu²⁺ (aq) + Fe²⁺ (aq)

Answer 1

For a spontaneous reaction E^o_cell must be positive
E^o_cell = E_cathode - E_anode
Ca ----------> Ca⁺² + 2e^- E_anode = -2.87 V
Cd⁺² + 2e^- ------> Cd E_cathode = -0.40 V
E^o_cell = -0.40 - (-2.87) = 2.47V , Hence first reaction is spontaneous
2Br^- + 2e^- -----------> Br₂ E_cathode= -1.07V
Sn⁺² --------> Sn + 2e^- E_anode= -0.14V
E^o_cell = -1.07 - (-0.14) = -0.93V , Hence the second reaction is not spontaneous.
The third reaction does not take place
Fe⁺³ + e^- ---------> Fe⁺²   E_cathode = 0.77V
Cu⁺ -----------> Cu⁺² + e^-  E_anode = -0.150V
E^o_cell = 0.77 - (-0.150) = 0.92V ; Hence fourth reaction is spontaneous.