# Stoichiometry and Yields

1. Sep 24, 2007

### salman213

The Title should actually be "Gravimetric Analysis"

srry about that but i cant change it now :(

1.
A 6.34-g geological sample, containing the mineral Boulangerite (Pb5Sb4S11) as the only lead-bearing compound, is subjected to chemical treatment in which the lead is quantitatively recovered as solid PbCl2. The mass of PbCl2 obtained is 3.80 g.
What was the percentage (by mass) of Pb5Sb4S11 in the sample?

2. n=m/MM
%yield= (actual yield over theoretical yield) * 100

3. Well im guessing the equation is something like

Pb5Sb4S11 -------> PbCl2(s)

how to get cl in there or SbS out :S

mass is given as 3.8g

I have no clue
can someone can get me started atleast?

Last edited: Sep 24, 2007
2. Sep 26, 2007

### chemisttree

If you knew the total number of moles of lead in the original sample could you use it to find out how many moles of $$Pb_5Sb_4S_{11}$$ were in the original sample?