Re: why does Calcium Carbonate CaCO3 LOWER the boiling point of filtered water?

Christine,

You are to be commended for your question. Isn't it great fun to do experiments in order to answer questions?! That is the way that science is supposed to be done... ask a question and find the answer through experiment and observation.

As you know, the addition of a solution to a solvent should, according to the prevailing body of knowledge, will cause a lowering of the vapor pressure of the pure solvent, depression of freezing point, an elevation in the boiling point and produces osmotic pressure. All of these solution properties are called colligative properties. The effect that a solute has on a solvent depends on whether the solute is an electrolyte or a nonelectrolyte and whether it is volatile or nonvolatile and how many solute particles are present in the solution. If you are interested in the effect that solutes have in solution, I would suggest that you do some reading on Raoult's law, colligative properties, van't Hoff factor, and solubility product (as calcium carbonate is sparingly soluble). Most high school chemistry textbooks will have information on these topics and all college/general chemistry texts would contain the information. Here are two references that you might want to peruse: (1) MODERN CHEMISTRY, pp. 450-456 [Nicholas D. Tzimopoulos, Ph.D., Holt, Rinehart and Winston, New York, 1990]; and (2) CHEMISTRY,5th Ed., pp. 513-557/Chapter 11 [Steven S. and Susan A. Zumdahl, both Ph.Ds, Houghton Mifflin Co., New York, 2000]. Some questions that came to mind in thinking about your question were: Was the boiling point of the pure solvent determined experimentally? Was the thermometer calibrated? Were the controls adequate? How many trial were done? What sort of reproducibility of results were obtained?(data analysis) If the experiment were repeated several times, say 3 to 5 times, with careful controls you might find that the results are quite different. When any measurement is taken, one must consider that the results obtained are flawed. This may be due to "consistent" errors (determinate) or "inconsistent" errors (indeterminate).

Anyway, I hope this gives you some insight. Do keep on asking questions and experimenting! You seem like a good student who wants to learn how things work. Kindest regards,

Charles Riner