Question

The “Zebra” cell was invented in 1985 in South Africa as part of the “ZEolite Battery Research Africa” project, and is used in all-electric municipal buses and other vehicles. It uses nickel and molten sodium as its electrodes. Its overall cell reaction is

NiCl₂(l) + 2Na(l) <--> Ni(s) + 2NaCl(l)

a)              Write the two half-reactions for this battery.

b)             Calculate the E^o for the Zebra cell (show your work).

c)              Are the reactants in this battery at room temperature when it is operating? Explain how you know.

Answer 1

Answer –

We are given reaction –

NiCl₂(l) + 2Na(l) <--> Ni(s) + 2NaCl(l)

a) We know two half reaction have oxidation and reduction reaction. In one reaction oxidation means loss of electron and one have reduction means gain of electrons.

In the given reaction there is NiCl₂ , means Ni has 2+ charge and it converted to Ni metal means it changes 2+ to 0, so it gets reduced and Na metal from 0 to +1 mean it gets oxidized.

So oxidation half reaction –

Na ------> Na⁺ + 1e^-

Reduction half reaction -

Ni²⁺ +2e^- -----> Ni

b) Now we need to look the standard reduction potential of each half reaction –

2Na ------> 2Na⁺ + 2e^-, E^ooxd = 2.714 V

Ni²⁺ +2e^- -----> Ni   E^ored = -0.25 V

Ni²⁺ + Na ------> 2Na⁺ + Ni ,   E^orxn = 2.464 V

c) No, at the room temp both the reactants are in solid state, but in the reaction there is showing both are liquid. We know Na and NiCl₂ both are solid and then have high melting point.