order of galvanic cell

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Ivanna_Tang_3B
Posts: 22
Joined: Wed Sep 21, 2016 2:58 pm

order of galvanic cell

Postby Ivanna_Tang_3B » Sun Feb 05, 2017 8:18 pm

How do we tell which are the reactants and products in a galvanic cell? is there a particular order?
For example,
C(gr)|H2(g)||H+(aq)||Cl-(aq)|Cl2(g)|Pt(s)
is products to reactants from inward to outward, or left to right?

Thank you!

Lucy Nakashima 1E
Posts: 21
Joined: Sat Jul 09, 2016 3:00 am

Re: order of galvanic cell

Postby Lucy Nakashima 1E » Sun Feb 05, 2017 8:29 pm

The right-hand electrode in the diagram is treated as the location where reduction occurs while the left-hand electrode is treated as the site of oxidation. The sign of the cell potential will tell you if the reaction is spontaneous in that direction or if the reverse reaction is spontaneous. So you would begin by writing the equation for the electrode on the right as a reduction half-reaction and you'd also write the oxidation half-reaction for the left-hand electrode. Then, you'd find the overall equation by balancing the number of electrons. If the overall cell potential is positive, your assumption was valid--reduction does occur at the right-hand electrode and oxidation at the left. If the cell potential is negative, however, it means the reverse reaction is spontaneous so you'd flip your equation.

Ranica Hortelano 2D
Posts: 9
Joined: Wed Nov 18, 2015 3:00 am

Re: order of galvanic cell

Postby Ranica Hortelano 2D » Sun Feb 05, 2017 8:41 pm

For cell diagrams the anode is always on the left side while the cathode is on the right side. Whatever is losing electrons is the anode and whatever is gaining electrons is the cathode.
For example, given Cu(s)|Cu 2+(aq)||Fe 3+(aq), Fe 2+(aq)|Pt(s) on the far left you always have the anode in solid form and following that you would put the corresponding ions (in this case Cu+2). You would then put || to indicate the salt bridge and then put the corresponding ions first for the cathode (here they are Fe 3+ and Fe 2+). On the far right (and the last thing in your cell diagram) should be the cathode in solid form. If there is no cathode or anode given in solid form you can put Pt(s).


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