How much P2O5 can be made from 85 g P and 80 g O2?

Question

The equation is: 4P + 5O2 → 2P2O5

Answer 1

Assume that all the phosphorus is used in the reaction (85g)

Find how much O₂ reacts with it.

85g P x (1mol P/ 123.88g) x (5mol O₂/ 4mol P) x (32g O₂/ 1 mol O₂) = 27.446g O₂.

Therefore the phosphorus will run out and only 27.446 grams of oxygen (out of the 80g O₂) will react.

The phosphorus is the limiting reactant and the oxygen is the excess.

Use the limiting reactant (85g of phosphorus) and find how much P₂O₅ can be made

I'm assuming they want this in grams.