review2f08v1 - McCord Exam 2 Review Topics Fall 2008 Which...

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Which Chapter/Sections are covered? All of Chapter 13 and Chapter 14 sections 1-6. Plus some general nomenclature stuff. Concentrate on the subject matter that was emphasized in class and on the homeworks. Come in mentally prepared to answer at least 25 questions, maybe more. Once again, you need to understand the theory and concepts – getting a homework question right does not necessarily mean you really understand the material. Ask yourself why you chose an answer. Try to explain the question to someone else. Nomenclature This is clearly stated in our textbook in section 2.9 of our book (p. 34-44). There is also a listing of polyatomic ions on one of my help sheets from the website. You will not get a ton of these type questions but you should expect a few. .. in class I asked. .. how many available (A) electrons for nitrate? You have to know the correct formula for nitrate to answer this question. The answer is 24 if you must know. Ionic vs Covalent Know the difference in these two types of bonding and compounds. Ionic compounds: These are all a continuous lattice of alternating cations and anions. We refer to their identities as formula units and NOT as molecules. They are held together by strong coulombic attractions which leads to nearly all (99.9%) of them being solids at room temperature. Not just solid but brittle solids – they will shatter if you whack them hard enough. If you want to melt them you need to get well above 500 ˚ C and for some, well above 1000 ˚ C. If you do get them melted, the resulting liquid WILL conduct electricity due to all the positive and negative ions flowing around. Let’s not say this: ionic bonds are the transfer of electrons. Yes, we’ve all heard that. The fact is simply there are lots and lots of ions (cations and anions) already out there in nature. These ions can and do find one another and they STICK together. THAT my friend is an ionic bond. As far as I’m concerned, the concept of electron transfer is best reserved for oxidation/reduction reactions and electrochemistry. To say that NaCl is made by taking one electron away from sodium and giving it to chlorine is to speak of an oxidation/reduction reaction – the result of which (in this particular case) is an ionic compound. My point is that you do NOT need to transfer any electrons to get an ionic bond or compound – you need IONS – cations and anions – find them where you may. Lattice Energies: Know what this is and what factors increase/decrease the values. Lattice energies really follow nicely with Coulomb’s Law which says that the potential energy ( V ) between two charges is proportional to the amount of the charges ( q 1 and q 2 ) divided by the distance between them ( r ): V q 1 q 2 r Charge is the bigger factor here. Why? Charge can easily double (+2) or even triple (+3). The distance, r , will depend on the size of the ions. The trends you learned in chapter 12 will help you here, but very rarely do you double or triple a ionic radius. Check page 596 on ionic
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This note was uploaded on 10/13/2008 for the course CH 301 taught by Professor Fakhreddine/lyon during the Fall '07 term at University of Texas at Austin.

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review2f08v1 - McCord Exam 2 Review Topics Fall 2008 Which...

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