Calculate the cell potential (E*cell) for the cell reaction using the standard reduction potentials for Hg and Ba

Question

I have been really confused on this and need to see steps to get through it and understand how to get the answer.

Answer 1

Hi Phoebe,

 

A quick answer is the question you have posted doesn't have enough information to provide an answer. The reaction in an electrochemical cell is a redox reaction, so you need to know what oxidation state the mercury is going to end up with (the barium only has one choice).

 

Once you have determined where the Hg ends up, you then compare  the standard reduction potentials for the Hg and the Ba cations to form the metal, and the more positive (or less negative) SRP will be the metal that gets reduced. That means you reverse the other reaction (changing the sign of that SRP) and add the two together to get E°_cell.

 

In summary:

1) write the reduction half reactions for each metal

2) look up the SRP for each reduction

3) keep the more positive value as is, leaving the E° alone

4) reverse the reaction with the more negative SRP, changing the sign of the E°

5) add the E° values to get E°_cell

 

Jim Scripko