Current Ionic Solution, Charges

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Homework Help Overview

The problem involves calculating the current passing through a sodium chloride solution based on the movement of Na+ and Cl- ions towards their respective electrodes over a specified time period. The context is rooted in electrochemistry and ionic conduction.

Discussion Character

  • Exploratory, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the calculation of current based on the number of ions and their charges, questioning the treatment of positive and negative currents. There are mentions of potential calculation errors and the direction of ion movement.

Discussion Status

Multiple interpretations of the current calculation are being explored, with some participants suggesting that the original poster's treatment of the charges may be flawed. There is acknowledgment of a possible mathematical mistake in the final summation, but no consensus has been reached on the correct approach.

Contextual Notes

Participants are considering the implications of opposite charges moving in different directions and how that affects the overall current calculation. There is a mention of a potential error in the mathematical handling of the charges, but specifics are not resolved.

PeachBanana
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Homework Statement



Current passes through a solution of sodium chloride. In 1.00 second, 2.68*10^16 Na+ ions arrive at the negative electrode and 3.92*10^16 Cl- ions arrive at the positive electrode. What is the current passing between the electrodes? Final answer must be in milliamperes.

Homework Equations



I = Q / Δt

The Attempt at a Solution



2.68*10^16 Na+ (1.6*10^-19 C) = 4.288 ma
3.68*10^16 Cl- (-1.6*10^-19C) = -6.272 ma

4.288 ma + (-6.272 ma) = -1.984 ma

Why is this incorrect?
 
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The ions aren't traveling in the same direction.
 
Bhumble said:
The ions aren't traveling in the same direction.

As far as I can tell OP accounted for that.

PeachBanana said:
3.68*10^16 Cl- (-1.6*10^-19C) = -6.272 ma

Buy a new calculator.
 
dQ/dt = I
opposite charges moving in opposite directions. Depending on the reference point both are either positive or negative.
Unless I'm missing something...
 
OP treats one current as positive, other as negative - that's equivalent.

And there is a simple math mistake in the final summation.
 
I don't see how that is equivalent since they are moving in opposite directions.
Say you have two charges one at point A and one at point B with one being positive and one being negative.
If they both move to opposite points then the magnitude dQ is 2. I don't see why this problem is different.
 
Sigh, you are right. Call it a senior moment.
 

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