Question

I am doing a science fair project on how different salts react in a salt water fuel cell car. I tested table salt, coarse salt, water softener, sea salt and rock de-icer. I couldn't figure out why the de-icer made the car run 2x as long? I think it is because the table salt, coarse salt and water softener are all Sodium Chloride (NaCl) but the de-icer is Potassium Chloride. I am only in grade 7 and find this fascinating. Do you know why this would make a difference? I think it might have something to do with the molecular weight difference OR the reaction the two different salts have wit

Answer 1

can U tell me the answer to this question first and fast please

Reggie accidentally left his books on top of his car before he left for class. The books stayed on top of his car while he was driving north on Oak Avenue. Then, when he made a sharp turn eastward onto Harris Lane, his books fell off the top of his car and onto the street.
Which of the following best explains why Reggie's books fell?

A. The Earth's magnetic field held the books on Reggie's car while he headed north. When he turned east, the magnetic pull faded, causing the books to fall.
B. The people that live on Harris Lane hate reading, which caused the books to fall.
C. Heat energy from the Sun caused Reggie's books to slide off the top of his car and fall.
D. When Reggie's car turned eastward, his books continued heading northward, causing them to slide off the top of his car and fall.

Answer 2

I find this interesting as well. First of all, any 'salt water fuel cell car' I have ever seen is actually just a battery that uses a zinc and copper strip with the salt water acting as the electrolyte. They operate exactly the same was as a potato clock (where the potato is the electrolyte). If you are using a car like this one, it is not a fuel cell, it is a battery:
http://www.amazon.com/OWI-Salt-Water-Fuel-Cell/dp/B004PBWQTS
It irritates me to no end that they call them 'fuel cells.' They are not.

I agree with you that the difference is because 3 of the 4 are NaCl and one is KCl, but I can't immediately answer why. Your guess as to a different molecular weight is a good idea, but KCl has a higher molecular weight, so if you use the same weight of each, you actually have fewer K and Cl ions, so I would think that would reduce its effectiveness. If you use the same volume, their densities are very close, so that wouldn't account for twice the running time.

I do have a couple of guesses as to the reason it would make a difference, but they are just guesses and not easy to explain (ion mobility, solvation shell around larger potassium ion, etc.). Since it's a science fair, put your hypothesis out there; say it's because KCl is different from NaCl, but you don't know why it has this result. If you really want an answer, you'll need to find a (better) expert in batteries.

My qualifications:
PhD candidate in Nanoscience Engineering, specializing in fuel cell materials.
I also have a minor in Chemical Engineering and have worked on battery materials.

Answer 3

@saynabahmed13
You're an idiot. If you don't want to be helpful, keep it to yourself.

Answer 4

Looking further, I find that there are some of these cars that are magnesium-air batteries that are sometimes (erroneously) called fuel cells. So, it may not be copper and zinc, but it is still functionally a battery.

This doesn't change the rest of what I said. And, knowing the reactions that occur in a magnesium-air battery, I still don't immediately see why the KCl is different from the NaCl.

Best of luck on your project!