Reef Chemistry Question of the Day #229 Electricity in water

[Randy Holmes-Farley]

Reef Chemistry Question of the Day #229

"Oh Crap" you exclaim, as you drop the end of a live extension cord into your aquarium. After hearing a quick pop under the stand, the tank goes dark and the sound of water going over your overflow slowly grinds to a halt.

Which of the following most likely happened (or, perhaps more correctly, happened the most times) in the water near the end of the extension cord?

A. An electron suddenly sensed an electric field, and started moving toward the positive electrode. The electric field intensity then started to fall. In 10 milliseconds the electric field actually reversed direction, and the electron started moving back the other way. In another 5 milliseconds, the electric field disappeared, and the electron was floating free again.

B. A sodium ion suddenly sensed an electric field, and started moving toward the positive electrode. The electric field intensity then started to fall. In 10 milliseconds the electric field actually reversed direction, and the sodium ion started moving back the other way. In another 5 milliseconds, the electric field disappeared, and the sodium ion was floating free again.

C. A chloride ion suddenly sensed an electric field, and started moving toward the positive electrode. The electric field intensity then started to fall. In 10 milliseconds the electric field actually reversed direction, and the chloride ion started moving back the other way. In another 5 milliseconds, the electric field disappeared, and the chloride ion was floating free again.

D. An electron suddenly sensed an electric field, and started moving toward the negative electrode. The electric field intensity then started to fall. In 10 milliseconds the electric field actually reversed direction, and the electron started moving back the other way. In another 5 milliseconds, the electric field disappeared, and the electron was floating free again.

Good luck!



































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[SDReefer]

I'm going to guess A.

 

[keddre]

Either A or D, so I'll guess A

 

[Greybeard]

Let's see if I can remember this stuff... Electrons are negatively charged...

A

 

[Beardo]

I will say C.
The negatively charged chloride ion would flow towards the positive electrode. There shouldn't be any free electrons floating around the tank.

 

[JimWelsh]

Both B and C, simultaneously. EDIT a minute later: C only. Sodium ions were moving too, but towards the negative electrode, and Randy said "positive electrode".

 

[billw]

I'd say CL- to the point of sale. electrode

 

[dragon99]

C

 

[jduong916]

The breaker jumped. Pull the extension cord out and flip the breaker back on and leave the electron and electric intensity to the scholars .

 

[JimWelsh]

The breaker jumped. Pull the extension cord out and flip the breaker back on and leave the electron and electric intensity to the scholars .

I hope it was the GFCI that tripped instead of the circuit breaker!

 

[Mark Gray]

I think D

 

[jduong916]

I hope it was the GFCI that tripped instead of the circuit breaker!

I dont trust those GFIs lol, they nuisance trip too much.

 

[Mark Gray]

The real answer is hey hold my beer while I fish this cord out of the water lol

 

[zsuzsu]

ahhh.......ya, ok

 

[zsuzsu]

can we just talk about girls instead

 

[Randy Holmes-Farley]

And the answer is...
"Oh Crap" you exclaim, as you drop the end of a live extension cord into your aquarium. After hearing a quick pop under the stand, the tank goes dark and the sound of water going over your overflow slowly grinds to a halt.

Which of the following most likely happened (or, perhaps more correctly, happened the most times) in the water near the end of the extension cord?

C. A chloride ion suddenly sensed an electric field, and started moving toward the positive electrode. The electric field intensity then started to fall. In 10 milliseconds the electric field actually reversed direction, and the chloride ion started moving back the other way. In another 5 milliseconds, the electric field disappeared, and the chloride ion was floating free again.

The chloride ion responds to the AC electric field near the two "electrodes", which exist where the copper wires in the end of the extension cord tough the water. For that fraction of the 60 Hz cycle that one electrode is positive, the chloride ion is attracted to it. Then the polarity reverses and the chloride ion is attracted toward the other electrode (assuming it didn't meet an untimely demise by reacting at the electrode surface to release an electron to the copper and become a neutral Cl atom). After the GFCI tripped, the electric field disappeared and the chloride ion was moving around "free" of this field. A typical GFCI trips in a reasonably small fraction of a second.

There are essentially no free electrons in aqueous (water) solutions, so answers A and D are incorrect. Unlike in metals, conduction in water is by larger ions than an electron.

Answer B is incorrect because a positively charged sodium ion is not attracted to a positively charged electrode.

Happy Reefing!