Soluble, or Not? Trivia Quiz

Answer: Salt

Salt is, of course, NaCl. Compounds of all of the alkali metals (lithium, sodium, potassium, etc.) are usually very water-soluble. So are the salts containing Cl-, Br-, and I- (though notable exceptions to this rule are Ag+, Pb+2, and Hg2 +2). This makes for a wonderfully soluble combination! The rocks and sand probably both consist of silicate minerals, which are very, very, very insoluble. You can enjoy your imagined lovely beach scene now.

Answer: No

If it were, all those poor oysters would be out in the cold! And, more importantly, that nasty whitish crud would dissolve away-- effortlessly. On the other hand, we can note the difference between The Chemist and The Geologist. The Geologist thinks that calcium carbonate is really soluble-- after all, it dissolves a whole lot faster than most of the other rock-forming minerals around.

The Geologist, in his or her muddy hiking boots, visits the rain-drenched jungles of Brazil, analyzes the soil, and finds almost no CaCO3, Ca+2 or CO3-2. Aha! CaCO3 is highly soluble! The Chemist, in his or her chemical-stained lab coat, on the other hand, plops a chunk of calcium carbonate in a beaker, stirs halfheartedly, watches as nothing happens, and thinks to himself, or herself, "Nothing happened! CaCO3 is not very soluble at all." So-- which one are YOU?

Answer: S 2- (sulfide)

Pyrite is iron sulfide, chalcopyrite is copper iron sulfide, galena is lead sulfide, cinnabar is mercury sulfide, and sphalerite is zinc sulfide. These minerals are usually deposited in hydrothermal veins, where the water carrying the dissolved minerals is either hot or slightly acidic, which increases solubility.

When the water nears the surface, it can be cooled or neutralized by interaction with rainwater, and the minerals precipitate. All right, I admit-- I'm really a geologist at heart!

Answer: No

Happily for you, barium sulfate is not soluble. If it were, the barium ion would be absorbed into your system, and you would die, and die miserably. Actually, barium sulfate is the lovely mineral barite. It looks just like calcite, but is much heavier. Most sulfates (SO4, with a charge of -2) are soluble, but those of Ca+2, Sr+2, Ba+2, Hg2 2+, and Pb+2, are not.

Answer: NO3-

There are no common exceptions to this rule. Now for the interesting stuff. High concentrations of nitrates in drinking water can cause "Blue Baby" syndrome. This is also less pronounceably known as "Methemoglobinemia." In babies, certain bacteria convert the nitrates into nitrites.

The nitrites react with hemoglobin molecules, reducing their ability to carry oxygen in the bloodstream. The oxygen-deprived baby turns blue, hence the name. This does not usually occur in adults for two reasons. First, adults secrete plenty of gastric acid, which kills the nitrate-to-nitrite-converting bacteria. Second, adults have high levels of an enzyme that converts the nonfunctional methemoglobin back into functional hemoglobin. Gotta love those enzymes.

Answer: AgF

AgF is generally considered soluble, but AgCl, AgBr, AgI are not. In fact, the solubility decreases in that order. This is a very useful property. If you have a solution containing the ions Cl-, Br-, and I-, you can precipitate out the different ions quite effectively. According to calculations I was forced to perform for my homework assignment, one can precipitate out 99.955% of the I- before AgBr starts to precipitate, and 99.82% of the Br- before AgCl begins to precipitate. Now, the really interesting information. AgCl, AgBr, and AgI turn black (from clear, white, or light yellow) with exposure to light. Yes, AgCl is what coats the film in your camera!

Answer: Benzene

Benzene, C6H6, consists of a ring of six carbon atoms, with one hydrogen attached to each. It is a nonpolar molecule. Buckyballs, which have a structure exactly similar to soccer balls (just imagine a carbon atom at each corner of the hexagons and pentagons) are also boring and nonpolar. In the realm of the confusing, benzene, benzyne, and benzone are completely different molecules. You have been warned!

This question previously and erroniously read, "Water is not always the best choice of solvent. Donald Huffman and Wolfgang Kratcher, the discoverers of Buckminsterfullerenes, aka Buckyballs, the soccer-ball-shaped carbon molecules, used which nonpolar solvent to dissolve the buckyballs?"

Player flopsymopsy kindly corrects me that, "In fact, Buckminsterfullerenes were discovered by a group of people, including Kroto, Curl, and Smalley who received the Nobel Prize for Chemistry in 1996. The (main) group did not include Huffman and Kratcher [correct spelling = Krätschmer] but they did invent techniques for producing fullerenes, which are a group of carbon molecules that includes several fullerenes and not just Buckminsterfullerenes." Thanks!

Answer: Fluorine

The gas fluorine is toxic, but non-toxic compounds such as sodium fluoride or sodium fluorosilicate are added to water as fluoride, in the process known as fluoridization. Toothpastes can also have fluoride added. Not all areas need to do this, since water naturally contains some fluoride. Only areas with low concentrations add fluoride, and it is not universally accepted as being "a good thing".

Answer: Nonpolar ones

Nonpolar substances dissolve in nonpolar solvents, and polar substances dissolve in polar solvents. This is why the cell membrane is such an effective barrier. Anything nonpolar that could dissolve in, and eventually cross, the membrane, probably wouldn't be water-soluble to be floating around in the water on either side. Substances dissolved in the water would probably be polar and not able to dissolve in the membrane. And the membrane wouldn't dissolve in the water because the water is polar, and the fatty acids of the membrane aren't. Clever, no?

Answer: Yes

Really, the Wicked Witch could have yelled, "I'm dissolving!" instead. But, in not-so-loving memory of the Wicked Witch, whenever it's raining outside, I'll tell people, "It's days like these that make me glad I'm not water-soluble." I hope you've enjoyed this quiz!