6. The density of sodium chloride is approximately 2.165 grams per cubic centime
ID: 3280324 • Letter: 6
Question
6. The density of sodium chloride is approximately 2.165 grams per cubic centimeter. The atomic mass of sodium is approximately 23.0. The atomic mass of chlorine is approximately 35.5 To this degree of accuracy, the atomic mass of an ion is the same as the atomic mass of an atom. Sodium chloride forms a "simple cubic" lattice which is to say that the atoms (or ions) lie on the corners of a cubic grid, like the integer-valued points on a Cartesian x-y-z coordinate system. Exactly half of the ions in sodium chlorine are sodium ions and the other half are chlorine ions. The sodium ions take up the same amount of space as the chlorine ions.Since a cube has six square faces, each sodium ion has six chlorine ions for neighbors. Each chlorine ion as six sodium ions for neighbors. How many sodium ions are there in 1.00 cubic centimeter of sodium chloride? What is the average distance between the center of one sodium ion and the center of a next-door neighbor chlorine ion? What is the average distance between the center of one sodium ion and the center of the nearest sodium ion? It may help to draw a picture or look at a cube as a model. If one sodium atom is at one corner of the cube, the nearest sodium atom would be at the opposite corner of a face of the cube. See the picture below a. b. C.Explanation / Answer
a) mol of NaCl in 1 cm3 = 2.165 gm/cm3 * (1mol NaCl / 58.44 gm) = 0.037046 mol/cm3
0.037046 mol/cm3 * (1mol Na+ / 1mol NaCl) = 0.037046 mol of Na+/cm3
1 mole has 6.023*1023 ions or particles
0.037046mol of Na+/cm3 * (6.023*1023 Na+ions / 1mol of Na+) = 2.2313*1022 Na+ions/cm3
So 2.2313*1022 Na+ ions are there in 1cm3 of NaCl
b) The next nearest neighbour Cl- atom will be aligned with the Na+ atom
so the center to center distance between them would be,
= rc + ra = rNa+ + rCl-
c) In NaCl , each Na+ ion has 12 Na+ ions surrounding and the average distance between the
center of one sodium ion to another sodium ion would be 2 r.
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