Question

What volume, in liters, does 128 grams of O2 occupy at STP?

a.89.6 L
b.22.4 L
c.67.2 L
d.44.8 L

Answer 1

The Ideal Gas Law

There are some important equations that we must know:

`PV=nRT`

• P = pressure
• V = volume
• n = moles
• R = Universal Gas Constant (8.31)
• T = temperature

`n=(m)/(M)`

• m = mass
• M = molar mass

Solving the Question

We're given:

• molar mass of O2 = 32.00 g/mol
• mass of O2 = 128 g
• T = 273 K (STP)
• P = 101.3 kPa (STP)

First, solve for n:

`n=(m)/(M)`

`n=(128)/(32.00)\\\\n=4`

Now, solve using the Ideal Gas Law:

`PV=nRT`

⇒ Isolate V:

`V=(nRT)/(P)`

⇒ Plug in given values:

`V=(4*8.31*273)/(101.3)\\\\V =89.6`

Answer

a. 89.6 L