How many moles of #PCL_5# can be produced from 22.0 g of #P_4# (and excess #Cl_2)#?
We need (i) a stoichiometric equation to represent the reaction:
If you want you can multiply out the coefficients to give integral numbers:
I find the multiplication a bit easier to deal with if you use the former equation.
And we need (ii), equivalent quantities of each reactant:
The chlorine gas oxidant is present in excess.
And thus, by the given stoichiometry with respect to phosphorus, we can make
This represents a mass of