![]() ![]() If you have any questions on ionic compounds refer to the sections on how to form ionic compounds and how to break apart ionic compounds. Make sure before you try to understand the examples and practice problems below that you know how to break apart and put together ionic compounds. If you only memorize the ions that are soluble, you only have to memorize half or less of the solubility table. MEMORIZATION TRICK: In AP or college classes you may have to memorize the solubility table. Typically they are only seen in AP and college courses and sometimes not even then. I also created an expanded solubility table that includes more ions you might see and work with in class. It is the simplest way to visualize, organize, and memorize the precipitation rules. For this reason we turn to what they call the PRECIPITATION RULES or the SOLUBILITY TABLE. Sometimes you will have to determine that for yourself. In a word question or chemical equation you will not always be shown whether a chemical is SOLUBLE (aq) or INSOLUBLE (s). You will need this sheet to record your data.What are the precipitation rules (what is the solubility table)? Lab Procedure Please print the worksheet for this lab. The plates and test tubes can then be washed in the normal manner. Use a squeeze bottle of deionized water to rinse the solutions into the beaker use the minimum amount of water you can, to avoid creating large volumes of waste solution. You may wish to have a beaker in your work area to collect waste while you are doing the experiment. Waste Disposal All of the solutions prepared in this experiment should be discarded in the waste container on the side shelf. They are not hazardous, and will fade in a few days. The spots will not appear for about 24 hours, as the ions are slowly reduced to the metal. #Precipitate rules skin#Silver solution will form dark spots on skin if spilled. chewing on fingernails, pens and pencils. Avoid putting anything in your mouth while in lab, ex. If you spill any on yourself, wash well with soap and water. Safety Some of the cation solutions are toxic. For anions, you will formulate a solubility rule which will allow you to guess what an appropriate spectator cation might be. In keeping with the usage of net ionic equations, only the cation, e.g., Ca 2+, will be listed in your data table. Therefore, the cations you will use will be solutions of their nitrate salts. Since the reactions will be done with ions in solution, the solutions must be prepared from compounds that are soluble. The results will be used to formulate a table of solubility rules. In this laboratory, you will perform a number of microscale chemical reactions to determine which anions form insoluble compounds with various cations. All of these compounds are soluble in water, and stable. Similarly, the iodide compound can be potassium iodide, KI, or sodium iodide, NaI. One does not find a bottle of lead(II) cations or iodide ions on a lab shelf! However, the reaction will work nicely regardless of whether the lead ion is introduced as lead nitrate, Pb(NO 3) 2, or as lead acetate, Pb(C 2H 3O 2) 2. The spectator ions must, of course, be present. They are used frequently in inorganic chemistry. Pb 2+( aq) + 2 I −( aq) → PbI 2( s) Net ionic equations are much simpler to write and interpret than total ionic equations. To express this, one may write a reaction in the form of a total ionic equation, as shown below: Nonetheless, the ions are not tied to a position or to a specific counterion (ion of opposite charge). The freedom is not absolute the positive ions will not all congregate in one portion of the solution. #Precipitate rules free#As noted previously, soluble ionic species are mobile and free to move independently of each other. This will be true when their charges ( q 1 and q 2) are opposite in sign and large. As an initial hypothesis, we can state that precipitates will form when the attractive force between ions is large. The solid compound, which has formed, is called a precipitate (noun). We say that the compound "falls out" of solution, or precipitates (verb). When the attractive force between opposite charged ions is great enough to overcome the energetically favorable interaction between the ions and water, the ions combine to form a compound that is not soluble in water. When ions of opposite charge encounter one another, F < 0, and the ions are attracted to one another. When the signs of the charges q 1 and q 2 are the same, F > 0 and the charges repel one another. * Water has a large dielectric constant, which reduces the electrostatic interaction between the particles. Ε (epsilon) is the dielectric constant of the solvent* ![]()
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