[mistertaylor92]

For a lab we constructed an electrochemical cell that consists of two compartments; one consisting of a zinc electrode submersed in a 0.15 M zinc chloride solution (the anode) and another consisting of a platinum electrode submersed in a solution that is 0.5 M in both potassium ferrocyanide (K4Fe(CN)6•3H2O) and potassium ferricyanide (K3Fe(CN)6)  (the cathode). I need to calculate Q for the reaction.

From what I understand, the representation of the cell is as follows:

Zn_(s) | Zn²⁺_aq(0.15M) || Fe(CN)₆^3-_(aq)(0.10 M), Fe(CN)₆^4-_(aq)(0.10 M) | Pt

And the overall reaction is as follows:

Zn_(s) + 2Fe(CN)₆^4-_(aq)    Zn²⁺_aq + 2Fe(CN)₆^3-_(aq)

Am I right to say that the reaction quotient for this reaction is equal to:

Q = [Zn²⁺]*[Fe(CN)₆^3-]²/[Fe(CN)₆^4-]²
   = (0.15 M)(0.10 M)²/(0.10 M)²
   = 0.15

The lab manual states that activities can be ignored. Thanks in advance.

[Borek]

In general looks good, but why 0.1 if 0.5?

[mistertaylor92]

My apologies that was a typo. The molarity of the iron compounds are both 0.1 M.