Reef Chemistry Question of the Day #163 Unknown Molecule

[beaslbob]

e

 

[beaslbob]

just to be different

 

[Randy Holmes-Farley]

And the answer is...B. Borate/Boric Acid

Very impressive answers for this difficult question.

The cheating way to get to the answer is to right click on the picture and search google images for it. It shows up in my borate article.

Some of the other answers are close but not quite. But they take quite a bit of chemical knowledge to rule out.

FWIW, I made the drawings in Chem 3D quite a few years ago, using the colors for atoms that were the default setting for it (if I recall correctly).

 

[Randy Holmes-Farley]

here's the borate article:

http://www.advancedaquarist.com/2002/12/chemistry

from it:

Boron in Seawater
In natural seawater, boron is present at about 0.41 mM (4.4 ppm total boron) and takes two different chemical forms. The predominate form is boric acid, comprising about 70% of the total boron present. Boric acid, B(OH)3, consists of a central boron atom and three hydroxyl groups arranged in a triangle (Figure 1). The second form is borate, B(OH)4-. It consists of a central boron atom and four hydroxyl groups arranged in a tetrahedron (Figure 1). It carries a net negative charge, while boric acid is neutral. These two forms can interconvert in less than a second, so the two forms are in chemical equilibrium with each other.

Figure 1. Space-filling molecular models of borate (left) and boric acid (right). The boron is yellow, oxygen is red, and hydrogen is blue.