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jesada
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Joined: 21 Aug 2017
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PostPosted: Mon Aug 21, 2017 5:40 pm    Post subject: voltaic cell gives unexpected voltage Reply with quoteFind all posts by jesada

A voltaic cell made with Cu l CuSO4 ll Fe l Fe(NO3)3 yielded a -0.420V when connected with black to Fe and red to Cu. The Cu has the lower Standard Reduction Potential(0.34V) so it should be oxidized( anode = black lead to meter) and the Fe(0.77V) should be reduced(cathode = red lead to meter) but this gives a negative voltage which means the flow of electrons( DC current is going in the opposite direction. (Both solutions were 1.0M)
This was done in "micro scale" with a black yarn string soaked in KCl as the salt bridge.
Seems weird. Any help out there?
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ChenBeier
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Joined: 27 Sep 2017
Posts: 20
Location: Berlin, Germany
PostPosted: Wed Sep 27, 2017 7:57 am    Post subject: Reply with quoteFind all posts by ChenBeier

wrong potential choosen

You choose Fe2+ to Fe3+ with 0,77 V

but you have Fe and Fe3+ in your cell it has -0,036 V

between there is also Fe and Fe 2+ with -0.402 V
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