chemistry help

Question

Calculate the emf of the voltaic cell: Concentration of Mg⁺² (anode)  is 0.00100 M and Fe⁺³ (cathode) is 0.100 M

 

unsure how to find this

Answer 1

You will need to use the Nernst Equation 

E_cell = Eº_cell - RT/nF lnQ

R = 8.314 J/mol-K

T = temp in K

n = # moles of electrons transferred

F = Faraday constant = 96485 C/mole electrons

Q = reaction quotient

 

If at STP, then this expression reduces to 

E_cell = Eº_cell - 0.0592/n log Q

 

So, you need to look up reduction potentials for Mg2+ and Fe3+, write the balanced half reactions, determine # electrons transferred, determine Eº_cell and the value of Q (0.001/0.1).  Then use the above equation to solve for E_cell