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Unformatted text preview: ENGR 220: Mid-Term Exam #1 Name:_________________________ Section_______ Spring 2009 R. Knight (Print) 60 mins. 1 Closed-book, closed-notes exam . Useful formulae, constants and a periodic table are attached (at the end). You may also use a calculator and ruler. Please show all working for full credit . 1. For the following questions choose the correct answer and/or fill in the blanks, as necessary. i) 2 pts. The electrons occupying the outermost filled shell of an atom are called __________ electrons. They are/are not (circle one) important when dealing with bonding. ii) 3 pts. For any bond to form, long/short (circle one) range attraction and/or (choose one) long/short (circle one) range repulsion is/are required. If it were the other way round then iii) 2 pts. Of the three primary bonds, only the ionic/covalent/metallic (circle one) bond is directional. iv) 2 pts. What is the predominant type of bonding for CH 4 ? (circle one) A. Ionic B. Hydrogen C. Covalent D. Van der Waals v) 3 pts. HCl has a higher/the same/lower (choose one) melting point than HF because vi) 3 pts . The reason solid ice floats in water is because (explain in terms of bonding). vii) 4 pts. The bonding in MgO and NaCl is predominantly ionic. The melting point of MgO is higher/lower (circle one) than that of NaCl because (explain using an equation) viii) 3 pts. For the HCP crystal structure, there are ___ atoms per unit cell because (show calculations) ix) 3 pts. The relationship between the cube edge length a and the atomic radius R in BCC is x) 5 pts . APF stands for ________________. The APF of BCC is . That number was calculated as...
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- Spring '09