Seawater question

[121]

I just came across this site. On part 5, http://oceanplasma.org/documents/chemistry.html it states, "Another way of saying this is that sea salts have constant composition. They almost always consist of 55% sodium ion, 31% chloride, 8% sulfate, 4% magnesium ion, 1% calcium ion, and 1% potassium ion."

How is the sea's salt 55% sodium and 31% chloride when it's 10,800ppm sodium and 19,400ppm Chlorine?

 

[disc1]

I just came across this site. On part 5, http://oceanplasma.org/documents/chemistry.html it states, "Another way of saying this is that sea salts have constant composition. They almost always consist of 55% sodium ion, 31% chloride, 8% sulfate, 4% magnesium ion, 1% calcium ion, and 1% potassium ion."

How is the sea's salt 55% sodium and 31% chloride when it's 10,800ppm sodium and 19,400ppm Chlorine?

You mean why is the smaller number going with the larger percentage?

The percentage is probably on a molar basis. The ppm that you list is a weight unit. Chlorine weighs a good bit more than sodium. So for the same number of atoms, a measurement in ppm is higher for chlorine.

 

[disc1]

For example if I dissolve 1mol of NaCl in 1L of water to make a 1M solution then the salt content is 50% sodium and 50% chlorine. 1mol of NaCl weighs 58.4g. There is 23g of sodium and 35.4g of chloride. So the solution is 23000ppm in sodium and 35400ppm in chloride.

 

[121]

Thanks Disc1, but after another look, I think they made a typo. It should be chlorine 55% and sodium 31% (30.6%).

 

[disc1]

In molarity units there is just a little bit more chloride than sodium in seawater. Chloride is the single most abundant element in seawater. Since chlorine weighs about 50% more than sodium, then looking at it by weight it is still the most abundant. So whatever units you are looking at, it should work out that way.

So I think you're right about the typo. Chlorine should win either way.