Cell Stoichiometry [Archive]

Nope

Nov12-09, 02:11 PM

1. The problem statement, all variables and given/known data

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.

2. Relevant equations

3. 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

Nov13-09, 03:23 AM

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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Nope

Nov13-09, 06:25 PM

Yes.
But when should I balance the electron?

Borek

Nov13-09, 06:45 PM

Sirsh

Nov15-09, 12:06 AM

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

Nov15-09, 05:05 AM

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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Sirsh

Nov15-09, 07:05 AM

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

Borek

Nov15-09, 07:11 AM

See IUPAC Green Book (http://www.iupac.org/reports/provisional/abstract05/GreenBook051206_prs.pdf), General Chemistry section, Other symbols and conventions in chemistry (2.10.1), (vi) States of aggregation.

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Nope

Nov19-09, 02:26 PM

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

Nov19-09, 03:36 PM

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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