Phosphorus burns in oxygen: P4 (s) + 5 O2 (g) → 2 P2O5 (s) If 4 mol of molecular phosphorus is available to react with 25 mol of O2, how many moles of the excess reactant will remain?

Question

a. 

1 mol

b. 

20 mol

c. 

5 mol

d. 

21mol

Answer 1

5 mol. Only 20 mol of O2 will react, leaving 5 mol left over.