Question

The phosphorus pentoxide used to produce phosphoric acid for cola soft drinks is prepared by burning
phosphorus in oxygen.
(a) What is the limiting reactant when 0.200 mol of P4 and 0.200 mol of O2 react according to

P₄ + 5O₂ --> P₄O₁₀

(b) Calculate the percent yield if 10.0 g of P₄O₁₀ is isolated from the reaction.

Answer 1

a) The equation is

P₄ + 5O₂ --> P₄O₁₀

It shows that one mole of P4 will react with 5 moles of O2 to give one mole of P4O10

So here we have 0.2 moles of P4 and O2

The limiting reaent is 0.2 moles of O2

0.2moles of O2 will react with 0.2/5 moles of P4 to give 0.2/5 moles of P4O10

The excess reagent is P4.

b) The molecular weight of P4O10 = 283.89 g/mol

So 0.2/5 moles = 283.89 X 0.2/5 grams = 11.36 grams

so the theoretical yield = 11.36

Actual yield = 10g

So % yield = Actual yield X 100 / Theoretical yield = 10 X 100 / 11.36 = 88.028 %