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General Chemistry at Penn State |
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CHEM 110 Fall
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Concentration Dilution Tutorials The Concentration Dilution Basic Skill Test is one of the most difficult Basic Skills. To help you be successful, we have prepared a series of On-line Tutorials that break down the questions into smaller parts to help you learn the basics needed to do the required Basic Skill Test. This link will take you to the Tutorials. You log in and take the test the same way you access the reviews for the Skills Check Tests. (In this case you will not get a review: you will access the actual tests.) THESE TUTORIALS ARE OPTIONAL FOR CHEM 110. You will not receive Chem 110 credit for taking them. Each Test has five questions. For a more detailed description of the first tutorial select this link. It gives you a good idea of what to expect (including sample problems) for the 5 questions for the first tutorial. The second tutorial is a repeat of the first tutorial except in MOST of the questions there will be EXTRA information. To answer the question correctly, you will have to read each question carefully and decide what is included in the question that is not needed to answer the question. The third tutorial will also be like the first tutorial except in this one, you will have to differentiate between the analytical concentration of a solute and the concentration of the ions that actually exist in solution. For example: if I prepare a 0.25M solution of NaOH, the analytical concentration of NaOH will be 0.25M. However, NaOH is a strong base (a strong electrolyte). That means in water, it will dissociate into Na+ and OH- ions. So in reality, my solution will contain 0.25M Na+ and 0.25 M OH- ions. If I have a CaCl2, solution with an analytical concentration of 0.25M the solution will be 0.50M in Cl- ions. In the third tutorial, you will be given either the concentration of ions or the moles of ions that end up in solution as a result of the dissolution process and you must determine the appropriate initial volume, molarity, etc. being asked for in the question after taking this dissociation into account properly. Again this will require careful reading of the question. Once you have completed the three tutorials successfully, you should be more prepared for the Chem 110 Concentration Dilution Basic Skill test that COMBINES all of these things. Each question may have BOTH extra information and involve stoichiometry of the dissolved species. This is why this Basic Skill is difficult. However, the problem solving skills needed to solve the questions in the Chem 110 Basic Skill Test are essential for success in scientific fields. |
