Question

A rigid 12.77 L tank was filled with Ar at 9.484 °C and 2.642 atm. A valve on the tank was opened and gas was allowed to escape. After closing it, the pressure and temperature was 1.948 atm and -12.24°C, respectively. How many grams of gas was released?

Answer 1

step 1: calculate initial number of moles
Given:
P = 2.642 atm
V = 12.77 L
T = 9.484 oC
= (9.484+273) K
= 282.484 K

find number of moles using:
P * V = n*R*T
2.642 atm * 12.77 L = n * 0.08206 atm.L/mol.K * 282.484 K
n = 1.455 mol

step 2: calculate final number of moles
Given:
P = 1.984 atm
V = 12.77 L
T = -12.24 oC
= (-12.24+273) K
= 260.76 K

find number of moles using:
P * V = n*R*T
1.984 atm * 12.77 L = n * 0.08206 atm.L/mol.K * 260.76 K
n = 1.183 mol

step 3: calculate moles of gas released
moles of gas released = 1.455 mol - 1.183 mol
= 0.272 mol

step 4: find mass of gas released

Molar mass of Ar = 39.95 g/mol

mass of Ar,
m = number of mol * molar mass
= 0.272 mol * 39.95 g/mol
= 10.87 g

Answer: 10.87 g