Question

A Chemist proposed adding powered zinc metal to a solution of Al³⁺ to precipitate Al metal at 25C.

a) If you srated with an Al³⁺ concentration of 0.2M and a Zn ion concentration of 0.0001M would the reaction become more or less electrochemically favorable?

b) If you added NaCl to the solution, how would the reaction favorability change?

c) Demonstrate electrochemically whether this would work or not at standard conditions and concentrations.

Answer 1

a. When the concentration of Al3+ and Zn ion are 0.2M and 0.0001M the reaction is less electrochemically favorable because at lower concentration the reverse reaction occurs spontaneously.

b. Sodium is a strong reducing agent and chlorine is a strong oxidising agent.When the solution of NaCl is added to reaction becomes more favourable.

c.Zn-->Zn^2+ 2e- (anode)

Al^3+ + 3e- -->Al (cathode)

Zn(s) +Al3+(aq)---> Zn2+(aq) + Al(s)

Nacl<---> Na^+ +cl-

Na^+ + e- ---> Na

2Cl- --->Cl2 +2e-