# Empiric formula

1. Feb 6, 2005

### danne89

I can't solve this: 1.63 g crom oxid gave 1.12 g crom during analysis. Calculate the empiric forumla of crom oxid.

% Cr = 1.12 : 1.63 * 100 = 68.7 %
% O = 100 - 68.7 = 31.3 %
Cr_xO_y
x:y = 68.7 : Cr : 31.3 : O
= 68.7 : 52 : 31.3 : 16
= 1.32 : 1.96
= 1 : 1
CrO
Which is completly wrong.

2. Feb 6, 2005

### chem_tr

Hello, try this: 1.32 and 1.96 can be further divided to give 1 and 1.485; this means that approximately 1:1.5 ratio is present. This is the same as 2 to 3, I mean Cr2O3

To sum up, dividing further to obtain a 1 in the series is the most important step here.

3. Feb 6, 2005

### danne89

Ahh! I understand!