Question

Consider a can of Barbasol shaving cream, which is 11 Oz or 325 mL. The propellant is mostly iso-butane (C4H10) which is pressureized to 2atm to deliver the product reliably to an external pressure of 1 atm. Assuming an external pressure of 1atm and temp of 298K, esetimate the amount of iso-butane remaining in an "empty" can of Barbasol. (Assume the propellant gas is ideal.

I really don't even know where to begin.

Answer 1

Volume of can given is 325 mL = 0.325 L

Now when the can is empty,it will have iso-butane vapours inside it at atmospheric pressure(=outside pressure).

n = PV/RT according to ideal gas equation

n= no. of moles of gas

P = pressure

V = volume

R = gas constant

T = temperature

= 1atm x 0.325L / (0.08206 atm.L/mol.K x 298K) = 0.0133 mol

isobutane = C4H10 , molar mass of isobutane = 12 x 4 + 1 x 10 = 58g/mol

mass = moles x molar mass = 0.0133 mol x 58g/mol = 0.77g

0.77 g iso-butane is remaining in the empty can