SI Exam 2 Practice Problems

SI Exam 2 Practice Problems - ENGR 145: Chemistry of...

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ENGR 145: Chemistry of Materials SI Practice Problems (Exam II) 1. As part of your ongoing research in molecular biology, you need rubidium chloride, a metal halide which, when applied to the cell surface, renders cells competent (able to take up DNA). You know that RbCl can form one of three complex crystal structures: rock salt, cesium chloride, or zinc blende , depending on surrounding conditions. A colleague has analyzed your sample and determined that both the cation and anion have coordination number of eight. a. Which complex crystal structure listed above does your sample of RbCl have? b. Circle all of the following symmetries which this crystal possesses. (The list may not be comprehensive.) C 4 C 5 C 3 C m Inversion c. Your chemical supplier has recently raised the price of RbCl and you are looking for an alternative. You suspect that the packing of RbCl plays a role in its ability to render cells competent. What is the cation / anion ratio range a complex crystal must have in order to adopt the same structure as your sample? d. With the radius ratio range from part c, determine the limiting atomic packing factors for this crystal structure. (HINT: the ions touch along the 111 direction)
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2. The following questions are related to crystal systems and basic crystal structures. a. Complete the blanks in the following table that summarizes three of the seven crystal systems. Crystal System Axial Relationship Interaxial Angles Monoclinic α = γ = 90° β 90° a = b c α = β = 90° γ = 120° α β γ 90° b. Some time in the future, you are working with a research group that has discovered a new metallic element. You name the element LeBronium after your favorite basketball player. Classify the crystal system of LeBronium knowing that all
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SI Exam 2 Practice Problems - ENGR 145: Chemistry of...

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