# Homework Help: Help with Chemistry problem

1. Oct 30, 2005

### parwana

Iridium has a face-centered cubic unit cell. The density of iridium is 22.61 grams per centimeter cubed. What is the diameter, in angstroms, of the iridium atom ?

Atomic weight of Iridium = 192.1

2. Oct 31, 2005

### Astronuc

Staff Emeritus
What work have you done.

With the information given and Avogadro's Number, one can find the number of atoms of iridium in one cubic cm.

Think how the atoms are arraged in the fcc lattice and how the lattice parameter relates to the atomic diameter (or radius).

3. Nov 3, 2005

### parwana

wouldnt u just divide the molar mass by 6.022 X 10^23 and times it by 4 since the fcc is made like that. After that I have no clue. Dont I have to convert density into g/angstroms?? Please help with this equation, I am going crazy over this.

4. Nov 4, 2005

### Gokul43201

Staff Emeritus
So far, this is correct. But what quantity is it that you have calculated by doing this ?

ie : What quantity does $$4* \frac{molar~ mass}{6.022 \cdot 10^{23}}$$ describe ?