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### Topic: Reaction Quotient for Electrochemical Cell  (Read 5955 times)

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#### mistertaylor92

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##### Reaction Quotient for Electrochemical Cell
« on: March 02, 2012, 06:52:19 PM »
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)63-(aq)(0.10 M), Fe(CN)64-(aq)(0.10 M) | Pt

And the overall reaction is as follows:

Zn(s) + 2Fe(CN)64-(aq)    Zn2+aq + 2Fe(CN)63-(aq)

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

Q = [Zn2+]*[Fe(CN)63-]2/[Fe(CN)64-]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

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##### Re: Reaction Quotient for Electrochemical Cell
« Reply #1 on: March 03, 2012, 04:56:13 AM »
In general looks good, but why 0.1 if 0.5?
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#### mistertaylor92

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##### Re: Reaction Quotient for Electrochemical Cell
« Reply #2 on: March 03, 2012, 06:02:05 AM »
My apologies that was a typo. The molarity of the iron compounds are both 0.1 M.