Posted by Dina on Thursday, February 4, 2010 at 7:15am.
Hello, I am having problem with two lab questions and was wondering if someone can help!
1. Calculate the percentage of the empty space in a facecentered cubic lattice, and show that it does not depend on the edge length of the unit cell ot on the size of the atoms in the unit cell. It says I need to find the edge length in terms of the radii of the atoms in the unit cell, the total volumme of the unit cell in terms of the edge length, and filled the volume from the total volume of the atoms in the unit cell.
What equation will you use to calculate heat of fusion of ice? The specific heat of water is 4.184J/ (g x c) and the heat capacity of your calorimeter is 1.0 x 10^1 J/C. Explain the reasoning behind your equation.

chemistry help!  bobpursley, Thursday, February 4, 2010 at 9:30am
There are four atoms per cell.
Packing factor: volumeatoms/volumecell
= 4*4/3 PI r^3 / s^3
Now, on any face diagonal, one has to have 4r, so 4r= s*sqrt2
packing factor: 16/3 PI 1/64 * 2sqrt2
= 1/6 PI sqrt 2= you do it.
b. I have no idea what you did, but suspect you melted ice of some mass.
Heatabsorbed=Hfusion*mass