How many moles of helium gas are contained in a 4.0-l flask at stp?

0.1784 moles of helium gas are contained in a 4.0-L flask at STP.

Explanation:

At STP. temperature of the helium gas = T = 273.15 K

At STP, pressure of the helium  gas = P = 1 atm

Volume of the helium  gas at STP  = V = 4.0 L

Moles of the helium  gas = n

Using an ideal gas equation :

n = 0.1784 mol

0.1784 moles of helium gas are contained in a 4.0-L flask at STP.