Reef Chemistry Quiz 2007

Welcome to the second annual reef aquarium chemistry quiz! 

This quiz provides you a way to test your reef chemistry skills, and likely learn something new at the same time.  It consists of 50 multiple choice questions relating to reef aquarium chemistry. It is automatically scored after you input your answers, and you will see the statistics of all who have submitted answers before you. Detailed explanations and links to more extensive articles on each topic are provided in an accompanying piece that will open after you complete the quiz.

Be forewarned, it is very hard! Last year, almost no one got every question correct.  Of the nearly three thousand entries, less than 1% got a score entitling them to the title of Master Reef Chemist, getting 90-100% correct.   Still, the quiz is not designed to be impossible, but to be a good test of your knowledge.  Most aquarists correctly answered between 25 and 60% of the questions.  If you want to take last year's quiz, click on this link.

All of the questions are based on topics we have discussed in the Reef Chemistry Forum, and all have been covered in articles intended for hobbyists. Nevertheless, I know of only a handful of reefkeepers whom I expect to get them all correct this year without looking up any information. Many aquarists with wonderful reef aquariums may get substantially less than half right. But you're up to the challenge, right?

The test can be open- or closed-book as you see fit; just interpret your score with that in mind.  To help guide your interpretation, here are my suggested score ratings:

90-100%
 Master Reef Chemist
80-89%
 Senior Reef Chemist
60-79%
 Reef Chemist
40-59%
 Apprentice Reef Chemist
26-39%
 Novice Reef Chemist
12-25%
 Neophyte Reef Chemist
0-11% 
 For heaven's sake, it's a multiple choice test!

Directions:

1. Select the box corresponding to the best response to each question.

2. If you take longer than a single session to answer all 50 questions (which is likely), then you can either:

Keep track of your answers on a separate sheet (maybe a printout of the quiz) and record them all at once.
Or…
Leave the window open on your computer with your answers recorded.

3. When you are finished recording your answers, hit the submit button. You will see your score, along with a detailed answer to every question. At that time, you will also see the statistics for all who have submitted answers before you.

If you have any questions, want to dispute any answers, practice up for next year or just want to gloat over your score, stop by the Reef Chemistry Forum here at Reef Central!

Happy Reefing!

Questions:

1. If you add soda water (seltzer; carbon dioxide in water) to normal seawater, which of the following will happen?

A. The pH and alkalinity will both drop
B. The pH will rise and the alkalinity will drop
C. The pH will drop and the alkalinity will stay the same
D. The pH will drop and the alkalinity will rise

2. Which of the following chemicals is most likely to immediately reduce a reef aquarium's ORP?

A. Ferrous gluconate (e.g., Seachem Flourish Iron)
B. Molecular iodine (I2, such as is present in Lugol’s iodine solution)
C. Hydrochloric acid (HCl; muriatic acid)
D. Magnesium sulfate (e.g., Epsom salt)

3. When using a refractometer to measure reef aquarium salinity, an aquarist is actually measuring what phenomenon?

A. The speed of sound moving through the sample
B. The speed of light moving through the sample
C. The speed of protons (H+) moving through the sample
D. The speed of salts moving through the sample

4. Which of the following is most likely to react with ozone to reduce the yellowing of reef aquarium water?

A. Ferric ion
B. Organic compounds with a methyl group
C. Organic compounds with an unsaturated carbon-carbon bond
D. Phosphate ion

5. Epsom salt is not optimal for making a large (200 ppm) boost to magnesium concentrations in a reef aquarium because it also contains which of the following:

A. Sodium ion
B. Epsilon ion
C. Chloride ion
D. Sulfate ion

6. Unlike many freshwater plant species, which primarily take up CO2 directly, most marine macroalgae can take up another ion from seawater in order to get the carbon dioxide that they need for photosynthesis.  Which of the following is this other ion?

A. Bicarbonate ion
B. Nitrate ion
C. Phosphate ion
D. Sulfate ion

7. At what pH in seawater would there be equal concentrations of carbonate and bicarbonate ion?

A. pH 5.85
B. pH 7.00
C. pH 8.20
D. pH 8.92

8. One water change that replaces 30% of the aquarium's water obviously removes 30% of a pollutant in that water (assuming that none is in the new water) and leaves 70% behind.  If, instead, a series of 30 water changes, each replacing 1% of the total water, are performed, how much of the original pollutant will remain?

A. 99%
B. 90%
C. 74%
D. 50%

9. All organic compounds contain which of the following atoms?

A. Carbon and hydrogen
B. Carbon and nitrogen
C. Nitrogen and phosphorus
D. Carbon and oxygen

10. The total alkalinity of seawater at pH 8.0 is closest to the concentration of which of the following in the water?

A. Carbonate
B. Chloride
C. Carbonic acid
D. Bicarbonate

11. Which of the following has never been shown to limit the growth of algae in the ocean?

A. Nitrogen
B. Sulfur
C. Iron
D. Phosphorus

12. At typical coral reef aquarium temperatures, the specific gravity of seawater is:

A. Higher than its density
B. Lower than its density
C. The same as its density
D. Either higher or lower than its density, depending on the barometric pressure

13. Which of the following chemicals is most likely to penetrate a reverse osmosis membrane (assuming no other filters are being used)?

A. Sodium ion (Na+)
B. Ammonia (NH3)
C. Magnesium ion (Mg++)
D. Chloride ion (Cl-)

14. What is the rank order of halides in seawater, from highest concentration to lowest?  ( >  means greater than)

A. Chlorine > Bromine > Iodine > Fluorine
B. Chlorine > Fluorine > Bromine > Iodine
C. Chlorine > Bromine > Fluorine > Iodine
D. Chlorine > Iodine > Bromine > Fluorine

15. In a balanced two-part calcium and alkalinity recipe, including my DIY recipe, why is it necessary to use two parts instead of combining them into a single additive?

A. Calcium carbonate will precipitate and will not redissolve in the aquarium
B. Calcium sulfate will precipitate and will not redissolve in the aquarium
C. You can mix them; I do it all the time
D. Magnesium sulfate will precipitate and will not redissolve in the aquarium

16. In a calcium carbonate/carbon dioxide reactor that is used to supply calcium and alkalinity to a reef aquarium, what is the molecular level function of the carbon dioxide?

A. It increases the concentration of magnesium, thereby increasing the solubility of the solid media
B. It increases the concentration of carbonate, thereby increasing the solubility of the solid media
C. It reduces the concentration of bicarbonate, thereby increasing the solubility of the solid media
D. It reduces the concentration of carbonate, thereby increasing the solubility of the solid media

17.What is the approximate concentration of water in seawater?

A. 999,965 ppm
B. 965,000 ppm
C. 99,965 ppm
D. 9,965 ppm

18. When pure calcium carbonate is deposited from solution, an exact ratio of calcium to alkalinity is used.  This ratio can then be used as the basis for balanced calcium and alkalinity additive systems that are designed to offset calcification losses in a reef aquarium.  These include two-part systems, limewater (kalkwasser) and calcium carbonate/carbon dioxide reactors.  This ratio is closest to which of the following?

A. 1 meq/L (2.8 dKH) of alkalinity for each 5 ppm of calcium
B. 1 meq/L (2.8 dKH) of alkalinity for each 10 ppm of calcium
C. 1 meq/L (2.8 dKH) of alkalinity for each 15 ppm of calcium
D. 1 meq/L (2.8 dKH) of alkalinity for each 20 ppm of calcium

19. When added to a calcium carbonate/carbon dioxide reactor, dolomite can be a suitable way to maintain existing magnesium levels.  It is not, however, a suitable way to raise low magnesium levels.  Which of the following is the primary reason it is not suitable for substantially raising magnesium?

A. Because it is too slow to dissolve
B. Because it adds to much sulfate to the water
C. Because it adds too much alkalinity to the water
D. Because it is too fast to dissolve

20. Which of the following is not likely to be a significant product of ozone reacting with the components of reef aquarium water?

A. Br3
B. BrOH
C. IOH
D. BrO3-

21. Which of the following is most likely to be selectively removed from seawater by skimming, in the exact chemical form described?

A. Iodide (I-)
B. Nitrate (NO3-)
C. Phosphate (PO3---)
D. A fatty acid

22. Which of the following, when dissolved in freshwater, is not a suitable way to provide both calcium and alkalinity to a reef aquarium?

A. Calcium acetate
B. Calcium oxide
C. Calcium chloride
D. Calcium hydroxide

23. On a refractometer, the symbol ‰ has what meaning?

A. ppt
B. ppm
C. Specific gravity
D. Refractive index

24. Tap water can contain many undesirable compounds.  Which of the following possible contaminants in tap water may not be removed by a properly functioning DI (deionization) resin alone?

A. Copper ion (Cu++)
B. Ammonia (NH3)
C. Phosphate (PO4---)
D. Chloramine (NH2Cl)

25.  Sea urchins have five continuously growing teeth with a complex mineral structure. Their teeth are amazingly rugged, and sea urchins have been known to eat through ferroconcrete piers, and lead-ensheathed deep-water telephone cables.  What is the highest concentration component of sea urchin teeth?

A. Calcium sulfate
B. Aragonite
C. High magnesian calcite
D. Organic polyimide

26. Many aquarists using GFO (granular ferric oxide) as a phosphate binder have reported significant precipitation of carbonates on the solid GFO and elsewhere in the system. Such precipitation can, for example, be a contributing factor in the caking of such materials and can coat other surfaces in the aquarium. This precipitation can also contribute to a detectable drop in alkalinity, and possibly pH, as it removes carbonate from the water column.

Dissolution of these precipitates with acid, accompanied by bubbling, indicates that these deposits are carbonates and are most likely calcium carbonate because it is supersaturated in most reef aquaria (and in the ocean).

Which of the following is the least likely explanation for the precipitation of calcium carbonate when using GFO?

A. Removal of nearly all of the phosphate from the water in the vicinity of the GFO may accelerate the precipitation of calcium carbonate.
B. Addition of soluble iron to the water in the vicinity of the GFO may accelerate the precipitation of calcium carbonate.
C. Removal of nearly all of the strontium from the water in the vicinity of the GFO may accelerate the precipitation of calcium carbonate.
D. Removal of many organics from the water in the vicinity of the GFO may accelerate the precipitation of calcium carbonate.

27. Which of the following is likely to be the most acutely (rapidly) toxic to a typical reef aquarium fish?

A. 2 ppm ammonia
B. 20 ppm nitrite
C. 50 ppm nitrate
D. 19,000 ppm chloride

28. Which of the following ions is nitrite?

A. NH4+
B. NO2+
C. NO2-
D. NO3-

29. Typical ocean water has a salinity of 35 ppt.  What portion of that 35 ppt is provided by sodium and chloride?

A. 30.2 ppt
B. 26.1 ppt
C. 22.4 ppt
D. 18.2 ppt

30. What is the rank order of carbon dioxide species in seawater at pH 8, from highest concentration to lowest?  (> means greater than)

A. Carbonate > bicarbonate > carbon dioxide/carbonic acid
B. Bicarbonate > carbonate > carbon dioxide/carbonic acid
C. Carbonate > carbon dioxide/carbonic acid > bicarbonate
D. Bicarbonate > carbon dioxide/carbonic acid > carbonate

31.When organisms grow, they use specific amounts of the various building blocks of matter.  Since most of the basic biochemicals of life are similar in different organisms (proteins, fats, DNA, etc.), the relative amount of certain atoms incorporated are similar.  In the case of phytoplankton, for example, this is called the Redfield ratio of certain nutrients taken up from the water, with the C, N and P shown below representing carbon, nitrogen, and phosphorus atoms, the relative amounts taken up by typical phytoplankton or algae are best represented by which of the following?

A. Carbon > nitrogen > phosphorus
B. Carbon > phosphorus > nitrogen
C. Nitrogen > carbon > phosphorus
D. Nitrogen > phosphorus > carbon

32. When limewater (kalkwasser) is added to a reef aquarium, it contributes to which of the following?

A. A deficiency of carbon dioxide
B. An excess of carbon dioxide
C. An excess of sulfate
D. A deficiency of sulfate

33. Suppose that the water in a reef aquarium has a nitrate concentration of 50 ppm and a new batch of artificial seawater at the same temperature has no nitrate in it.  If 10% of the water in the aquarium is replaced by the new water, the final nitrate in the aquarium will be closest to which of the following values?

A. 48 ppm
B. 45 ppm
C. 25 ppm
D. Not enough information is provided to properly answer

34. Suppose that the water in a reef aquarium has an alkalinity of 2.5 meq/L (7 dKH), and a new batch of artificial seawater at the same temperature has an alkalinity of 4 meq/L (11 dKH).  If 10% of the water in the aquarium is replaced by the new water, the final alkalinity in the aquarium will be closest to which of the following values?

A. 2.65 meq/L (7.4 dKH)
B. 2.85 meq/L (8.0 dKH)
C. 3.05 meq/L (8.5 dKH)
D. Not enough information is provided to properly answer

35. Suppose that the water in a reef aquarium has a pH of 8.4, and a new batch of artificial seawater at the same temperature has a pH of 7.9.  If 10% of the water in the aquarium is replaced by the new water, the final pH in the aquarium will be closest to which of the following values?

A. 8.37
B. 8.35
C. 8.33
D. Not enough information is provided to properly answer.

36. Suppose that the water in a reef aquarium has a specific gravity of 1.0264.  If 10% of the water in the aquarium is replaced by pure freshwater at the same temperature, the final specific gravity in the aquarium will be closest to which of the following values?

A. 1.0264
B. 1.0246
C. 1.0237
D. Not enough information is provided to properly answer

37. Suppose that a liquid calcium additive comprised of calcium chloride in water is used to boost the calcium level in a reef aquarium.  It is described on the bottle as containing 100,000 mg/L calcium ion.  In order to boost the calcium level by 50 mg/L, how much must be added to an aquarium system containing 100 gallons of water? (Note that 1 gallon = 3.785 liters.)

A. 512.2 mL
B. 378.5 mL
C. 226.4 mL
D. 189.3 mL

38. Suppose that a reef aquarist living in New York City has a big New Year's Eve party. Dozens of folks crowd around his tank, admiring it. Just before midnight, he notices something unusual in his aquarium that was caused by the party goers, but everyone swears they didn't mess with the tank. What is the most likely thing that he observed?

A. The calcium level was 25 ppm higher than normal.
B. The alkalinity was 0.5 meq/L (1.4 dKH) lower than normal.
C. The pH was 0.3 pH units lower than normal.
D. The ORP was 25 mV lower than normal.

39. Nitrite can interfere with some nitrate test kits.  If nitrite is present at 2 ppm, and the real nitrate is 5 ppm, then nitrite's interference with some kits that suffer this interference can make the nitrate appear to be which of the following?

A. Much higher than 5 ppm
B. Between 1 and 5 ppm
C. Undetectable
D. Uninterpretable, as the colors will be wrong

40. If limewater (kalkwasser) is used over a few days to boost the alkalinity in a reef aquarium by 1 meq/L (2.8 dKH), the calcium level will have risen by how much?

A. 5 ppm
B. 10 ppm
C. 20 ppm
D. 30 ppm

41. What is general hardness (GH)?

A. A measure of alkalinity
B. A measure of calcium only
C. A measure of magnesium only
D. A measure of calcium plus magnesium

42. Suppose that fluoride is present in seawater with a salinity of 35 ppt at a concentration of 1.000 mg/L.  When the sample is at 77°F, which of the following is closest to the fluoride concentration in ppm?

A. 1.000 ppm
B. 0.977 ppm
C. 1.026 ppm
D. 35 ppm

43. Compared to seawater at pH 8.5, how many more free protons (H+) are there in seawater at pH 7.5?

A. Ten times as many
B. Twice as many
C. Equal numbers
D. One-tenth as many

44. Which of the following units is not equivalent when measuring alkalinity?

A. 5.6 dKH
B. 2 meq/L
C. 125 ppm calcium carbonate equivalents
D. None; they are all the same.

45. If the concentration of nitrate ions in a reef aquarium is 25 ppm, what is that same concentration in ppm-N (ppm nitrate nitrogen)?

A. 5.6 ppm-N
B. 7.6 ppm-N
C. 11.3 ppm-N
D. 21.4 ppm-N

46. The prefix “micro” on a unit of measure means which of the following?

A. One-millionth of the unit
B. One-thousandth of the unit
C. One-hundredth of the unit
D. One thousand of the units

47. How many U.S. teaspoons are in a U.S. tablespoon?

A. Two
B. Three
C. Four
D. Five

48. In a chemical recipe mixing two ingredients, which of the following values for the smaller ingredient will not result in its same concentration in the solution as the others?

A. 0.02 w/w
B. 2 weight percent
C. 2 mg/g
D. 20 g/kg

49. What is the most likely chemical identity of the primary chemical that initially precipitates and then dissolves as it is further mixed into the aquarium water when adding limewater (kalkwasser) to seawater?

A. Calcium carbonate
B. Calcium hydroxide
C. Magnesium hydroxide
D. Magnesium sulfate

50. Last chance to up your score!

Hydrogen sulfide is most likely present in which of the following forms in seawater at pH 8.2?

A. H2S
B. HS-
C. HS+
D. S--

To reveal the answers and a page showing your score as well as the score of all that have taken the test, hit the 'Submit' button below.

If you have any questions about this article, please visit my author forum on Reef Central.




Reefkeeping Magazine™ Reef Central, LLC-Copyright © 2008

Reef Chemistry Quiz 2007 (Questions) by Randy Holmes-Farley - Reefkeeping.com