4p + 5O2 -> P4O10 ; the percent yield of PO4O10 when 6.20 g of phosphorus burns into excess oxygen is 67.0%. What is the yield of P4O10?

   36.9 g

Explanation:

P4 + 5O2 = P4O10  Balanced equation

moles P4 present = 23.9 g x 1 mole/123.88 g = 0.193 moles

moles O2 present = 20.8 g x 1 mol/32 g = 0.65 moles O2

From balanced equation, mole ratio O2 : P4 is 5:1.  Is 0.65 moles O2 5x 0.193 moles?  NO.  You don't have enough O2.

O2 is limiting in this reaction.

theoretical moles of P4O10 = 0.65 moles O2 x 1 mole P4O10/5 moles O2 = 0.13 moles P4O10

mass of P4O10 produced = 0.13 moles x 283.9 g = 36.9 g

the correct answer is:

a. formation of precipitation

i'm wiling to try and you : )