## adeniyta 3 years ago Hello, I am trying to find the density of iridium, but I do not understand how to find the volume using the information provided; could someone please help me with this problem? Question: What is the density of iridium metal? (Ir: 192.2 g/mol; face-centered cubic with 3.83x10^-8 cm edges).

1. JFraser

You know 1 mole of iridium has a mass of 192.2g. How much should a single atom of iridium weigh? $Mass = (\frac{192.2g}{1mol})*(\frac{1mol}{6.022*10^{23}atoms})$ Below is the figure for a face-centered cubic cell. There are 6 half-atoms and eight 1/8th atoms that make up this cell. How many atoms total is that? (4) Since you konw what a single atom weights, find out how much the atoms inside the cell weigh, and divide by the volume of the cell (since it's a cube, vol = length^3). I get about 22.3g/cm^3

Thank you- this was very helpful.

I don't understand how you found the volume, could you please show the math you did?

4. JFraser

the face centered cell is a cube. You are given the length of one edge of the cube. Volume is length x width x height. All 3 sides are the same, so the volume of the cube is (length)^3