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SCAN0050 - /’ 3 Iridium has a face-centered cubic unit...

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Unformatted text preview: /’_\ 3. Iridium has a face-centered cubic unit cell with an edge length of 383. 3 pm. Calculate the density of solid iridium. Do the same as #1 you already have 1 13—5 6314 x 107 pm convert this to cm3 1042me cm pm 10'2 m l 10’6 Now we need the mass of four atoms 4 atoms .lr x 3] mole/6 022 x 1023 atoms x 192 22 g/mole —~ 1 2768 X 102 g3rams Density 1s g/cm3 so— —_ 1.2768 x 10‘3‘g/563i4 x 1033 cm3 = 22.67 g/cm3 5.6314X107pm3x( )3 5.63l4x107x10”3(’x cm3 : 5.63i4x10—33cm3 4. A metallic solid with atoms in a face-centered cubic unit cell with an edge length of 392 pm has a density of 21.45 g/mL. Calculate the atomic mass and the atomic radius of the metal. Identify the metal. Given 1, we can find I since i=1 divided by root 8 I 139 pm = 1.39 x 10‘8 cm If we have density and a volume we can find the mass of four atoms which can lead us to the molar mass The volume is obtained by cu3bing the edge length. (392 pm)3 — 6 0236 x 107 pm3 — 6 0236x 10 33c m3 6.0236x 10333616 x21 45g mL= 1 292x 100“ g This is the mass of four atoms, so the mass of one atom is 1.292 x 10‘“ g/4 = 3.23 x 1033 g/one atom we want this per mole 3.23 x lO'ng/atom x 6.022 x 1023 atoms/mole ~= 194.52 g/mole This answer is close to Pt and it has that density, so it must be right. ...
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