[syd]

Hi I'm a little confused as to what this question is asking me, exactly.  We did a class experiment on the stoichiometric point of Pb(NO3)2 (aq) + K2CrO4 (aq)  PbCrO4 (s) + 2 KNO3.  Our concentration of K2CrO4 was .0442 M and we all used 12.00 mL of it.  The concentration of the lead salt was .100 M, and I used 3.00 mL, so my millimoles of pb was .300.

At the end of some of my questions it's asking me to figure out the mole ratio of K2CrO4 to Pb(NO3)2, but it also says (from graph, do not round off).  We graphed the class data with our ppt mass against the number of millimoles of pb salt.  My stoichiometric point is right at .520 millimoles of lead salt.

Does this mole ratio have anything to do with the average maximum mass of precipitate we got?  For example, figure out how many moles of pb are in that versus how many moles were the K2CrO4 solution??

Thanks!

[syd]

Actually I think I got it.  Millimoles of the potassium chromate was .530, and millimoles of my lead at the stoichiometric point was .520, so the ratio is just about 1.02