What is the pressure of a 1.0 L flask containing 0.12 g of He at 25°C? (R= 0.0821 L atm/mol K)

To solve this question, we should use the ideal gas law: PV=nRT, where P represents the pressure (in atm in this case), V represents the volume (in L), n represents the number of moles of gas, R is the ideal gas constant, and T represents the temperature (in K).

Before we can plug our values into the equation, we must convert so that our units cancel out. First, we should convert our temperature from degrees Celsius to degrees K.

25°C + 273.15 = 298.15K

Next, we should convert the 0.12 g He to moles using the molar mass of He.

0.12 g He * (1 mole He/4.003 g He) = 0.029978 mol He

Now, we can plug in the values into the equation and solve for the pressure.

PV = nRT

P = (nRT)/V

P = (0.029978 mol He * 0.0821 L*atm/mol*K * 298.15 K)/(1.0 L)

P = 0.73 atm

Therefore, the correct answer is 0.73 atm.

Hope this helps!