Question

A 5 L flask containing N2 at 1 bar and 25°C is connected to a 4L flask containing N2 at 2 bar and 0°C. After the gases are allowed to mix keeping both flasks at their original temperature, what will be the pressure and amount of N2 in the 5L flask assuming ideal gas behaviour?

Answer 1

After the two are allowed to mix,

Total volume = 5L + 4L = 9L
and,
PV=constant

therfore, P₁V₁ =P₂V2

For flask 1, 1bar $\times$5L = P₂ $\times$9L (after mixing)
P₂=0.54 atm (1 bar = 0.986atm)

similarly for flask 2 , P₃ = 0.84 atm.

After mixing the two flask will have same pressure, that is the total pressure,P

P = P₂ + P₃ = 1.42atm.

and the pressure of N₂ in flask 1 will be 1.42 atm.

Amount :

n = $\frac{PV}{RT}$
$\frac{1.42\times 5}{0.82\times 298}$
= 0.29moles.