RXN Stoichiometry? (yields etc)?

Question

Consider the reaction 5P4O6 + 8I2 4P2I4 + 3P4O10. How many grams of iodine must be added to 4.26 g of P4O6 to have a 8.00 % excess of iodine?

---------- g I2

What is the theoretical yield of P4O10?

----------g P4O10

How many grams of P2I4 would be isolated if the yield is 87.5%?

-------- g P2I4

Answer 1

Moles P4O6 = 4.26 g / 219.8914 g/mol =0.01937

Moles I2 needed = 0.01937 x 8 /5 = 0.03100

0.03100 x 108/100 =0.03348 moles I2

Mass I2 = 0.03348 mol x 253.809 g/mol =8.498 g

Moles P4O10 = 0.01937 x 3 /5 = 0.01162

Mass P4O10 = 0.01162 mol x 283.895 g/mol = 3.299 g

87.5 = grams x 100 / 3.299

grams = 2.887 g