Posted by Tammy on .
Which one of the gollowing represents the theoretical yield, in grams, of precipitate for the double displacement reaction if 25.0 mL of 1.75 M aqueous calcium nitrate is added to 15.0 mL of 1.50 M sodium phosphate?
This is a limiting reagent problem.
3Ca(NO3)2 + 2Na3PO4 ==> Ca3(PO4)2 + 6NaNO3
moles Ca(NO3)2 = M x L
moles Na3PO4 = M x L
Using the coefficients in the balanced equation, convert moles Ca(NO3)2 to moles Ca3(PO4)2.
Same process, convert moles Na3PO4 to moles Ca3(PO4)2.
Probably the answers for moles Ca3(PO4)2 will not agree which means one of them is wrong; the correct answer, in limiting reagent problems is ALWAYS the smaller value and the reagent producing that value is the limiting reagent.
Finally, convert moles Ca3(PO4)2 from the previous step to grams. g = moles x molar mass.