Chem help (1 Viewer)

[jilly12]

I was doing this question and I kept getting 0.51V which I concluded as spontaneous but the answer said -0.51V does anyone know where I went wrong? Cause the book said the half-reaction with the higher standard potential goes as written and the other is reversed. (Sorry I cant show my working out its on my iPad and I'm writing this on my computer). If someone could show me their working out it would really be helpful. Thanks.

 

[wizzkids]

All electrode potentials are defined as reduction potentials. The reduction potential of Cu²⁺ to Cu(s) E^o is 0.34 V and the reduction potential of Hg²⁺ to Hg(l) E^o is 0.85V. The reaction is non-spontaneous, mercury metal will not displace copper ions from a solution of copper sulfate. Here is the working.

 

[jilly12]

All electrode potentials are defined as reduction potentials. The reduction potential of Cu²⁺ to Cu(s) E^o is 0.34 V and the reduction potential of Hg²⁺ to Hg(l) E^o is 0.85V. The reaction is non-spontaneous, mercury metal will not displace copper ions from a solution of copper sulfate. Here is the working.
View attachment 43694

Thank you, also Can I ask how you figured out the net reaction first, would you not need to find the half-reactions beforehand? Is there another strategy or method?

 

[wizzkids]

Thank you, also Can I ask how you figured out the net reaction first, would you not need to find the half-reactions beforehand? Is there another strategy or method?

The net reaction is like a hypothesis- I'm asking this question at the beginning with a chemical equation, "Can mercury be oxidised to mercury 2+ ions and copper 2+ ions be reduced to copper in a spontaneous reaction?" The answer is, "No."