Answer:
54.0 mol
Explanation:
Given data:
Initial pressure in tank = 42.0 atm
Initial moles in tank = 119.4 mol
Final pressure in tank = 19.0 atm
Final number of moles = ?
Solution:
According to ideal gas equation,
PV = nRT
P = n (RT/V)
pressure is directly proportional to the number of moles when R , T and v are kept constant.
Pâ/nâ = Pâ/nâ
Now we will put the values.
42.0 atm / 119.4 mol = 19.0 atm / nâ
nâ =  19.0 atm Ă 119.4 mol  / 42.0 atm
nâ = Â 2268.6 atm. mol /42.0 atm
nâ = 54.0 mol