How Do You Calculate Equilibrium Concentrations in a Redox Reaction?

[cliffordlim]

Homework Statement

Fe2+and Cr2O72- react as follows: 6Fe2+ + Cr2O7 2− + 14H + >>> 6Fe3+ + 2Cr3+ + 7H2O.

The equilibrium constant for the reaction is 1×10^57. Calculate the equilibrium concentrations

of the iron and chromium species if 10 mL each of 0.02M K2Cr2O7 in 1.14M HCl and 0.12M FeSO4

in 1.14M HCl are reacted.

Homework Equations

The Attempt at a Solution

https://physicsforums-bernhardtmediall.netdna-ssl.com/data/attachments/97/97696-2f7ec586395970f64d734682baf6f166.jpg

This is the solution provided . I still don't understand as Cr3+ is 0.02M in the equation as the question give is K2Cr2O7 is 0.02M > does it mean 0.02M of Cr2O72- ? Same goes to iron .

 

[Borek]

I still don't understand as Cr3+ is 0.02M in the equation as the question give is K2Cr2O7 is 0.02M > does it mean 0.02M of Cr2O72-

Elaborate please, I have no idea what you mean.

Chances are you are forgetting about dilution, but that's just a wild guess.

 

[mjc123]

I think there is a mistake in the text; when it says "At equilibrium 0.02 mol/L Cr₂O₇^2- has reacted..." that should be 0.01 mol/L Cr₂O₇^2-. Is that the problem? I think the expression here is unclear. But then you say "same goes to iron". Are you just forgetting about dilution, as Borek suggests?