How many miles of P4 are needed to produce 10.5L at STP

Question

The balanced equation is 

8P4 + 3S8 ---> 8P4S3

Answer 1

I'm going to assume the question states: 

How many moles of P₄ are needed to produce 10.5 L of P₄S₃ at STP?

First, use the ideal gas law to find moles of product produced, since the volume is for liters of P₄S₃. 

 

PV=nRT

Solve for n

n=PV/RT

 

P = 1 atm

V = 10.5 L of P₄S₃

R = 0.0821 L⋅atm/K⋅mol

T = 273.15 K

 

n = (1 atm)(10.5 L)/(0.0821 L⋅atm/K⋅mol)(273.15 K)

n = 0.468 moles P₄S₃

 

Then use the balanced equation to convert moles of P₄S₃ to moles of P₄. This is a 1:1 ratio.

 

0.468 moles P₄S₃ x (8 moles P₄)/(8 moles P₄S₃) = 0.468 moles P₄