What amount in moles of phosphorus produces 6.45 mol of tetraphosphorus hexoxide? P4 + O2 → P4O6?

Answer 1

P4 + 3 O2 → P4O6

(6.45 mol P4O6) x (1 mol P4 / 1 mol P4O6) = 6.45 mol P4

Answer 2

The first step is to get a balanced equation:

P4 + 3O2 → P4O6

Next, use the coefficients in the balanced equation to construct a molar ratio between P4 and P4O6:

P4 is to P4O6 ---> 1 : 1 molar ratio

Finally, we write  ratio and proportion:

1 is to 1 as x is to 6.45

x = 6.45 moles of P4 required.

Notice that the O2 plays no role, so the act of balancing seems to have played no role. That should not matter. ALWAYS balance the equation first.