Reef Chemistry Question of the Day #260 Loss of Elements by Evaporation

[Randy Holmes-Farley]

Which of the following elements (in any form) is least likely to leave a normal reef aquarium by evaporation from the top of the water?

A. Hydrogen
B. Sulfur
C. Nitrogen
D. Potassium
E. Oxygen
F. Iodine
G. Bromine
H. Carbon

Good luck!

























.

 

[Jose Mayo]

D. Potassium

 

[mgreenough]

Edit ignore my post i just reread it - least likely

 

[dragon99]

Potassium? Because it's an akali metal

I'm interested in the explanation on this one though

 

[AdamNC]

D - Potassium

“Potassium is one of the alkali metals. The alkali metals are the elements that make up Group 1 (IA) of the periodic table. The periodic table is a chart that shows how chemical elements are related to one another. The alkali metals also include lithium, sodium, rubidium, cesium, and francium. They are among the most active metals.

Potassium is so active that it never occurs free in nature. It always occurs in compounds, combined with other elements. It was first prepared in pure form in 1807 by English chemist Sir Humphry Davy (1778-1829). Davy used a new method of isolating elements that he had invented, electrolysis. In electrolysis, an electric current is passed through a molten (melted) compound. The electrical current breaks the compound into its elements.”



Read more: http://www.chemistryexplained.com/elements/L-P/Potassium.html#ixzz5DMNRBy6M

 

[redfishbluefish]

G. Br


EDIT TO ADD: Darn dyslexia...I read it "most" likely to evaporate....Br is the only one that will!

 

[JimWelsh]

I can't think of a single volatile potassium compound. D. Potassium.

 

[marke]

E O2

 

[marke]

E O2

 

[Alfrareef]

Iodine.

 

[Chuk]

D: Potassium
Its one of the most stable components on the table so least likely to volatalize (think I may have made up a word here).

 

[bluewill]

d Potassium
will not precipitate thru evaporation, although i wouldn't think Bromine would either

 

[Randy Holmes-Farley]

And the answer is...D

Which of the following elements (in any form) is least likely to leave a normal reef aquarium by evaporation from the top of the water?
A. Hydrogen
B. Sulfur
C. Nitrogen
D. Potassium
E. Oxygen
F. Iodine
G. Bromine
H. Carbon

There are no forms of potassium that would be present in a reef tank that will evaporate. It is only present as K+ ion, and it won't evaporate. In general, anything with a charge on it won't evaporate. The very unusual forms of potassium that might evaporate (methyl potassium, and even potassium metal) will instantly decompose in water.

Going through the other choices, I'm only listing one or two forms that evaporate, but for each, many exist:

A. Hydrogen (comes off as water, H2O, evaporates)
B. Sulfur (comes off as H2S (hydrogen sulfide) and dimethylsulfide (CH3-S-CH3) which is often associated with a "small of the ocean")
C. Nitrogen (comes off as N2 gas and ammonia, NH3)
D. Potassium winner!
E. Oxygen (comes off as water, H2O)
F. Iodine (comes off in organic forms, such as CH3I; the ocean loses hundreds of millions of kg each year as CH3I)
G. Bromine (comes off in organic forms such as CH3Br, which is made by algae)
H. Carbon (comes off as CO2 and organics; almost any smell above a reef tank contains carbon)

Happy Reefing.