9. The unit cell below is best described as what type of crystal structure? 1 po
ID: 1083205 • Letter: 9
Question
9. The unit cell below is best described as what type of crystal structure? 1 pody-centered cubic (2) simple cubic (3) trigonal(4) face-centered cubic 10. Which of the following characteristics indicates the presence of weak intermolecular forces in a iquid? (1) a low heat of vaporization pressure (4) a high boiling point (2) a high critical temperature (3) a low vapor 11. The intermolecular forces present in CHsOH include which of the following? 1. dipole-dipole ll.ion-dipole . dispersion n. hydrogen bonding (1)I, ll, lll, and IV (2) l and Ill (3)I, , and (4) l and 12. Potassium bromide, KBr, crystallizes like NaCl in a face-centered lattice. The ionic radi of K and Br ions are 133 pm and 195 pm, respectively. Assuming that all Br ions are positioned in the face and corners of the unit cell, while the K ions are positioned along the edge alternating between anions, calculate the length, d, of a unit cell edge. Br K+ (1) 230 pm (2) 328 pm (3) 523pm (4) 656 pm 13. The number of atoms in a body-centered cubic unit cell is (1)1 (2)2 (3)4 (4) 8Explanation / Answer
As you have indicated to problem 12.
Answer of 12 is D) 656 pm
Solution:
KBr has FCC structure. So, each edge will consist of one K & one Br.
So, edge length = diameter of K + Diameter of Br
= 2 * 133 pm + 2 * 195 pm
= 656 pm.
13. The body-centered cubic (bcc) has a coordination number of 8 and contains 2 atoms per unit cell.
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