Reef Chemistry Question of the Day #280: Which is the best analogy of ion spacing in seawater?

[Randy Holmes-Farley]

Reef Chemistry Question of the Day #280:

Which of the following is the best analogy of ion spacing in seawater?

A. The ions in seawater are spaced like a 20 ducks on a 1 acre pond
B. The ions in seawater are spaced like 4 people on a 747 jet
C. The ions in seawater are spaced like 2 ice cubes in a glass of water
D. The ions in seawater are spaced like 3 kittens in a single carrier.

Yes, I know, it's an odd way to ask the question, but I think many reefers have little intuition of what the relevant spacing is and I hope we can learn from it.

Hint: There was a relevant Reef Chemistry question of the day about 5 years ago. lol


Previous Reef Chemistry Question of the Day:

Reef Chemistry Question of the Day #279: Ions sticking to calcium carbonate

Reef Chemistry Question of the Day #279 Which of the following two ions are least likely to stick to a bare calcium carbonate surface in a reef aquarium? A. Lithium B. Magnesium C. Calcium D. Strontium E. Phosphate F. Nitrate Good luck! Previous question of the day...

www.reef2reef.com

 

[Adam1985]

A

 

[hollow6210]

B

 

[Miami Reef]

Hmm. Can I pick 2 choices?

C or D. I’m more inclined to say C, but I wouldn’t be surprised if it’s D.

 

[Randy Holmes-Farley]

You can pick however many you want, or a different answer if you think a different analogy is better.

 

[JimWelsh]

According to Pilson, there are 1147.59 mM (per liter) of ions of the major constituents in seawater at S=35. Avogadro's number (number of things in a mole of things) is 6.022E+23. So, there are 6.19E+23 ions in a liter of seawater. If we arranged them spaced evenly in a cube, then along each edge of that cube, there would be the cube root of 6.19E+23 = 8.84E+07 ions. Since that edge is 1.0E+08 nm long, then the ions are 1.0E+08/8.84E+07 = 1.13 nm apart, on average. The chloride ion is 0.181 nm in size, and the sodium ion is 0.227 nm. Sulfate is 0.242. Magnesium is relatively small at 0.065 nm. Still, given that you have a bunch of things that are about 0.2 units in size spaced 1.13 units apart, then I'll go with C, I guess.

EDIT: I had to laugh out loud when, after posting this, I Googled "average distance between ions in seawater", and the QOTD that Randy mentioned above was the first link! I had forgotten about that exchange.

 

[MnFish1]

A. The ions in seawater are spaced like a 20 ducks on a 1 acre pond

Would say no - thats random - Though I suppose herd mentality keeps some together
But - there are multiple ions in seawater - so it would be like asking about multiple kinds of ducks.

B. The ions in seawater are spaced like 4 people on a 747 jet
Thats probably decided by the airline - so . no
C. The ions in seawater are spaced like 2 ice cubes in a glass of water
I guess it depends on the size of the glass - so - though I was going to pick this - its the same scenario - depends on the size of the ice and the size of the glass
D. The ions in seawater are spaced like 3 kittens in a single carrier.
3 kittens - like the ions in seawater seem to me - like they are in the space they are in. Like Calcium and Alkalinity - if they get too close - there are problems - i.e precipitation

 

[BroccoliFarmer]

A. The ions in seawater are spaced like a 20 ducks on a 1 acre pond

Would say no - thats random - Though I suppose herd mentality keeps some together
But - there are multiple ions in seawater - so it would be like asking about multiple kinds of ducks.

B. The ions in seawater are spaced like 4 people on a 747 jet
Thats probably decided by the airline - so . no
C. The ions in seawater are spaced like 2 ice cubes in a glass of water
I guess it depends on the size of the glass - so - though I was going to pick this - its the same scenario - depends on the size of the ice and the size of the glass
D. The ions in seawater are spaced like 3 kittens in a single carrier.
3 kittens - like the ions in seawater seem to me - like they are in the space they are in. Like Calcium and Alkalinity - if they get too close - there are problems - i.e precipitation

Although heard mentality makes sense...wouldnt you have a similar problem with ice cubes in a glass of water? The ice cubes would naturally float to the top thus eliminating almost all of the separation. Further more, the surface tension of the water would make the cubes have a tendency of 'being stuck' to each other.

 

[mizimmer90]

Reef Chemistry Question of the Day #280:

Which of the following is the best analogy of ion spacing in seawater?

A. The ions in seawater are spaced like a 20 ducks on a 1 acre pond
B. The ions in seawater are spaced like 4 people on a 747 jet
C. The ions in seawater are spaced like 2 ice cubes in a glass of water
D. The ions in seawater are spaced like 3 kittens in a single carrier.

Yes, I know, it's an odd way to ask the question, but I think many reefers have little intuition of what the relevant spacing is and I hope we can learn from it.

Hint: There was a relevant Reef Chemistry question of the day about 5 years ago. lol


Previous Reef Chemistry Question of the Day:

Reef Chemistry Question of the Day #279: Ions sticking to calcium carbonate

Reef Chemistry Question of the Day #279 Which of the following two ions are least likely to stick to a bare calcium carbonate surface in a reef aquarium? A. Lithium B. Magnesium C. Calcium D. Strontium E. Phosphate F. Nitrate Good luck! Previous question of the day...

www.reef2reef.com

A picture is worth a thousand words! Here's a little video I just made, simulating seawater to help with intuition:

Ions are shown with their van der Waals radii, and water is shown as red/white sticks.

Concentration of some common ions (I tried to get it close to seawater):
Cl - 570 mMol (green)
Na - 490 mMol (red)
Mg - 55 mMol (blue)
Ca - 11 mMol (magenta)
K - 11 mMol (yellow)

 

[MnFish1]

Although heard mentality makes sense...wouldnt you have a similar problem with ice cubes in a glass of water? The ice cubes would naturally float to the top thus eliminating almost all of the separation. Further more, the surface tension of the water would make the cubes have a tendency of 'being stuck' to each other.

Yes - my problem with C was a glass of water could be 1 liter, 12 oz, etc - and ice cubes change shape - so - there is also that variable.

 

[MnFish1]

According to Pilson, there are 1147.59 mM (per liter) of ions of the major constituents in seawater at S=35. Avogadro's number (number of things in a mole of things) is 6.022E+23. So, there are 6.19E+23 ions in a liter of seawater. If we arranged them spaced evenly in a cube, then along each edge of that cube, there would be the cube root of 6.19E+23 = 8.84E+07 ions. Since that edge is 1.0E+08 nm long, then the ions are 1.0E+08/8.84E+07 = 1.13 nm apart, on average. The chloride ion is 0.181 nm in size, and the sodium ion is 0.227 nm. Sulfate is 0.242. Magnesium is relatively small at 0.065 nm. Still, given that you have a bunch of things that are about 0.2 units in size spaced 1.13 units apart, then I'll go with C, I guess.

EDIT: I had to laugh out loud when, after posting this, I Googled "average distance between ions in seawater", and the QOTD that Randy mentioned above was the first link! I had forgotten about that exchange.

Curious though - there is no information about the size of the glass or the ice cubes - so how do you know which dimensions to use?

 

[CrunchyBananas]

Curious though - there is no information about the size of the glass or the ice cubes - so how do you know which dimensions to use?

I think you're overthinking it, one could be asking what size pond too, no? 1/10 an acre, or 3 acres?
I believe he's talking in generalities and is referencing a normal 16 oz (or so) average glass of water, and the ice cubes in a static state (not melting I mean). You can think of them as two neutrally buoyant balls floating around in a pint glass if that helps you grasp the concept a bit better.

also, I think C.

 

[shootingstar_reef]

I think A? maybe c and d in a lower rank. D could kinda be like A but in a different sized space

 

[BroccoliFarmer]

All of the above based upon which quantum state the ions are in? Yeah, I’m watching end game

 

[MnFish1]

I think you're overthinking it, one could be asking what size pond too, no? 1/10 an acre, or 3 acres?
I believe he's talking in generalities and is referencing a normal 16 oz (or so) average glass of water, and the ice cubes in a static state (not melting I mean). You can think of them as two neutrally buoyant balls floating around in a pint glass if that helps you grasp the concept a bit better.

also, I think C.

Perhaps - But - My comment came from trying to calculate using mathematical methods to figure out which one is correct. Since it's supposed to be an analogy, and Since Ions can move around, up, down, etc - I pick D as the closest. . I do not think one can make some of the calculations and apply that to this these analogies.

 

[IslandLifeReef]

Ok, I'll say A, because they are free to move around, getting closer and further apart due to temperature changes. Unlike the 747, the pond temperature is controlled by nature.

 

[Randy Holmes-Farley]

EDIT: I had to laugh out loud when, after posting this, I Googled "average distance between ions in seawater", and the QOTD that Randy mentioned above was the first link! I had forgotten about that exchange.

I remembered it, but looked it up to try to estimate some analogies correctly. lol

 

[Randy Holmes-Farley]

A picture is worth a thousand words! Here's a little video I just made, simulating seawater to help with intuition:

View attachment 2890245


Ions are shown with their van der Waals radii, and water is shown as red/white sticks.

Concentration of some common ions (I tried to get it close to seawater):
Cl - 570 mMol (green)
Na - 490 mMol (red)
Mg - 55 mMol (blue)
Ca - 11 mMol (magenta)
K - 11 mMol (yellow)

That's very cool! Thanks for posting it. Are you a professional modeler of some sort?

I would just caution that the apparent spacing in 2D is closer than the reality of 3D, if you just took the ratio of water and ions and mixed them together in 2D (not sure if that's what you did or not). Extrapolating to 1D (just spacing all the water and ions on a line), the relative spacing error would much worse (about 1 ion per 55 water molecules in a line).

 

[dennis romano]

I'll go with C or D. The ions have to be in close proximity. With an ionic bond, the electrons in an atom's outer shell are transferred from one to another. Two ice cubes would represent a simple two element molecule such as H20. A covalent bond which shares electrons between multiple elements would be like the cats.

 

[MnFish1]

I have re-thought this 100 times lol. Unless (which obviously there is) I'm missing something obvious - All of the analogies have some problems - BUT I'm going to change my vote to the 747.

There are different people in the plane - plus the cabin staff. Usually when the plane is nearly empty, the people (let's call them the ions) can move around freely. And the Empty seats could represent the water molecules in the shell bound to the ions - Since there (to my understanding) far more water molecules than ions in seawater. So I'm changing from the cats to B.