Step-by-step explanation:
The given data is as follows.
 P = ?, V = 10 liter
 n = 1.4 moles, T = 
 = (20 + 273) K = 293 K
As per the ideal gas equation, PV = nRT. Therefore, putting the given values into the formula as follows.
 PV = nRT
 
 
 P = 3.36 atm
 = 3.4 atm (approx) 
Thus, we can conclude that the pressure in the flask in units of atmospheres is 3.4 atm.