# Cell Stoichiometry

## Homework Statement

Determine the mass of sodium deposited at the cathode of a molten NaCl(l) electrolytic cell if 10.0 A flow through the cell for 2.00h.

## The Attempt at a Solution

For the mole ratio,
Na+ +e --> Na
2Cl- --> Cl2 + 2e
Should I balance the electron ? 2Na+ +2e --> 2Na
or I use Na+ +e --> Na
Thanks

Borek
Mentor
Na+ + e- -> Na will do.

Do you know Farady's law of electrolysis? Do you know how to calculate charge given current and time?

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Yes.
But when should I balance the electron?

Borek
Mentor
Not sure what you mean - sodium reduction reaction is written is already balanced.

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methods

You balance the half equations, Then identify which is oxidised and reduced, then you add the electrons to the specific sides (RHS reduction, LHS oxidisation). but if Na+(aq) + e- --> Na(s).

Just check your standard reduction potentials chart and you'll see.

Borek
Mentor
Na+(aq) + e- --> Na(s).

Na+(aq) + e- -> Na(s) - state of matter symbol should be listed in plain text, not subscript nor anything.

Just check your standard reduction potentials chart and you'll see.

These are of no use here - you are already told what is the reaction that goes on - reduction of sodium.

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methods

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The super script was an accident, But I dont see why i cannot use sub script for them?

Borek
Mentor
See http://www.iupac.org/reports/provisional/abstract05/GreenBook051206_prs.pdf [Broken], General Chemistry section, Other symbols and conventions in chemistry (2.10.1), (vi) States of aggregation.

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methods

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Not sure what you mean - sodium reduction reaction is written is already balanced.

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Oh, I mean like when we write net ionic equation,we will balance electron ,but do we do the same thing for this question, and then use that amount of electrons to the calculation?
Like 2Na+ 2Cl- +2e --> 2Na(s) +Cl2 + 2e

Borek
Mentor
You don't have to - we are interested only in sodium and we need just sodium half reaction. Balanced - but half reaction only.

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methods