Sulfur trioxide, SO3, is produced in enormous quantities each year for use in the synthesis of sulfuric acid.

Question

S(s) + O2(g) -> SO2(g)
2SO2(g) + O2(g) -> 2SO3(g)

What volume of O2 (g) at 350 degrees Celsius and a pressure of 5.25 atm is needed to completely convert 5.00g of sulfur to sulfur trioxide?

Answer 1

The long way, but perhaps easier to understand, is to convert 5 g S to moles, then to mole O2 needed and moles SO2 produced in the first equation. Take the mole SO2 produced in equation 1 and use that to determine moles oxygen from equation 2. Add the two to find total moles O2. Then use PV = nRT to find volume O2. Check my thinking.

Answer 2

Okay, I know this is 10 years old. I just found it because I had this exact same problem on a homework assignment. Here's what I got after a bit of work:
V = Volume of O2

350.°C -> 623 K

5.00 g S / 32.06 g S = 0.156 mol S

0.156 / 2 = 0.078 mol O2

0.156 + 0.078 = 0.234 mol O2

V = (0.234 * 0.08206 * 623) / 5.25 = 2.28 L O2

I'm pretty sure this is right. I hope it helps whoever comes next!

Answer 3

I forgot to include the equations I used.

I used this one:
PV = nRT

But we were solving for volume, so I changed it to this:
V = nRT / P