I’m doing a science fair project , in which i plan to test how different acidities of water will effect the lifespan of triops (these little aquatic creatures). What kind of acid should i use? (and nothing like coke, or orange juice, or battery acid that will kill them immediately)
Boric and phosphoric acid could be used for more acidity and ammonia as a base.
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You can use weak acid acidify the water. Example of weak acid are acetic acid found in vinegar, citric acid found in lemons, and boric acid.
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HCl is used to adjust the pH of swimming pool water. The commercial quality HCl is called muractic acid. Experiment with a very dilute HCl solution.
You could also use a very dilute solution of HNO3.
Your options include HCl, HNO3, and H2SO4…all are strong acids (complete ionization to H+ and Cl-, NO3- or SO4-2).
You want to use a strong acid to minimize the amount of un-ionized acid in the water. For example, if you use acetic acid, when you have the desired H+ concentration, you will have appreciable amounts of un-ionized acetic acid in solution.
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go with vinegar, but it is a little more difficult to calculat the acidity of a vinegar solution, if you just add a little acid at a time, it won’t kill them (a drop) no matter what acid you choose. Strong acids are easier to calculate the pH (you don’t say what grade your in) unless your just using full pH range indicator paper, then it won’t matter.
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In my opinion different type of acid can actually have effect on the survival of aquatic species and not only acidity itself, though, of course, at very low pH, triops will die regardless of the acid used. Despite of what you say, well why don’t you try a very dilute solution of sulfuric acid (maybe 10 mL of concentrated sulfuric acid in one liter? Arrange a series of containers with fresh water and adjust the pH to 7, 6.5, 6.0, 5.5 and 5.0 by adding few drops of the diluted solution (Always mix well before measuring pH), and have a separate container with original unaltered water for reference. Then introduce the specimen in each container and see what happens. then re-adjust pH as needed every 2 hours as needed.
If you do these things you will be exploring the toxicity of sulfuric acid on aquatic life. In real life, polluted water may contain various types of acid such as hydrochloric, phosphoric, citric, nitric and carbonic. Besides, there are hydrolizable salts, such as sulphates and chlorides, which alter pH wihtout being acids themselves, and all this is without considering the CO2 content and the bacteria developing in the water. So , it is more complicated than you imagine. The kind of acid have also an effect. Some acids will only complex certain micronutrients, while others may even hydrolize proteins such as nitric acid.
You know what? Water chemistry is a whole career by itself.
So, you will be only investigating a very small portion of a big problem-
For measuring pH I recomend you an electronic pH meter, the pH indicator paper may not be suitable for you experiment. If you don’t have one, well buy a cheap one at http://www.thomassci.com you may find a pocketsize pH meter at $30 or so.
http://www.thomassci.com/catalog/product/1733
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