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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: Damiano0707 on December 07, 2017, 02:43:54 PM

Title: Electrochemistry problem
Post by: Damiano0707 on December 07, 2017, 02:43:54 PM

Immersing a bar of Fe in a water solution 0,100M PbCl2, 0,100M MnCl2, 0,100M MgCl2 and 0,00100M HCl, what happens?
A)Mn deposits on the bar
B)Mg deposits on the bar
C)Nothing happens
D)Pb deposits on the bar

Hi
I have some doubts about this problem. I know I have to apply Nernst equation but, in case of hydrogen, I have not the concentration of the oxidated state and the reduced one. Besides I have no temperature.

Title: Re: Electrochemistry problem
Post by: Borek on December 07, 2017, 03:19:38 PM

Start with just reactivity series, Nernst equation becomes important when potentials are very similar.

Title: Re: Electrochemistry problem
Post by: Damiano0707 on December 07, 2017, 03:38:56 PM

 Thanks for the answer. But I can't understand what happens by just reactions

Title: Re: Electrochemistry problem
Post by: Damiano0707 on December 07, 2017, 04:37:07 PM

I think I need to use potentials

Title: Re: Electrochemistry problem
Post by: Borek on December 07, 2017, 06:20:20 PM

I can't stop you from doing in the hard way, it is your choice if you want to waste time on things that can be done much faster and easier. Please remember reactivity series is based on the redox potentials, really no need to calculate exact potential to know whether Mg can deposit or not.

You can always assume room temperature (59.9 mV/n) and 1 atm for H₂.