Cell Diagrams

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Cell Diagrams

Postby vpena_1I » Sat Feb 22, 2020 8:39 pm

Is there a way of telling what species are reactants/products when given just the cell diagram? I can tell once I see the standard potentials, but is there a way to know without searching them up?
For example, 6L.3(b) gives:

I thought the species in bold were given in the form Reactants|Products, but is this only true when there is a comma, not a line between them?

Vincent Leong 2B
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Re: Cell Diagrams

Postby Vincent Leong 2B » Sat Feb 22, 2020 10:14 pm

I think the cell diagram only gives the knowledge necessary to tell what species are being reduced and oxidized. From knowing this, we can deduce what species are the reactants and products. To get to the overall reaciton, I recommend writing out the full half reactions, balancing each half reaction with coefficients, and finally cancelling out the number of electrons.

Ex. we know Cl2 + 2e --> 2Cl- and H2 --> 2h+ + 2e from the cell diagram; reduction/cathode on the right and oxidation/anode on the left; balance these two equations and then write the overall reaction from adding the 2 half reactions. finally, you know the reactants and products.

Kayli Choy 2F
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Re: Cell Diagrams

Postby Kayli Choy 2F » Sun Feb 23, 2020 10:30 am

Additionally, the double line in the middle of the cell diagram represents the salt bridge, while the single lines represent interfaces.

Lizette Noriega 1H
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Re: Cell Diagrams

Postby Lizette Noriega 1H » Sun Feb 23, 2020 10:38 am

My TA was informing us that the standard order for the elements in the cell diagram goes as following:

solid|gas|aqueous || aqueous|gas|solid

But it would be difficult to establish their phase accordingly. The question should provide you with any information you need while keeping in mind that one line calls for a phase change, while the double represents a salt bridge, and a comma allows for the separation of multiple species in one particular phase. Also, keep in mind that the reduced reaction (cathode) is on the right while the oxidized reaction (anode) is on the left.

Anika Chakrabarti 1A
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Re: Cell Diagrams

Postby Anika Chakrabarti 1A » Sun Feb 23, 2020 11:19 am

The diagram tells us that the elements on the left side of || are involved in oxidation and the elements on the right are involved in reduction. With this information, you can figure out each half-reaction and determine which are reactants and products based on whether electrons are being lost or gained.

Radha Patel 4I
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Re: Cell Diagrams

Postby Radha Patel 4I » Sun Feb 23, 2020 12:21 pm

When we know that the left side of || is oxidation and the right of || is reduction, we can then determine how to design the half reaction. For example we see that in order for H to be oxidized it needs to lose electrons, so it would go from
H2-->H+ with a balanced reaction of H2-->2H+ +2e-

Connor Chappell 2B
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Re: Cell Diagrams

Postby Connor Chappell 2B » Sun Feb 23, 2020 12:26 pm

A single line between compounds on the same side of a double line indicates a change in the physical oxidation state of the compound. For example, solid Fe being oxidized into Fe^2+ in solution would be denoted as { Fe(s)|Fe^2+|| }.

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