Current Ionic Solution, Charges

[PeachBanana]

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?

 

[Bhumble]

The ions aren't traveling in the same direction.

 

[Borek]

The ions aren't traveling in the same direction.

As far as I can tell OP accounted for that.

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

Buy a new calculator.

 

[Bhumble]

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...

 

[Borek]

OP treats one current as positive, other as negative - that's equivalent.

And there is a simple math mistake in the final summation.

 

[Bhumble]

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.

 

[Borek]

Sigh, you are right. Call it a senior moment.